The catalytic conversion of greenhouse gases, such as carbon dioxide and methane, into high-value-added chemicals/fuels (i.e., formic acid, methanol, ethylene, etc.) is recognized as a cost-effective tactic for achieving the "dual-carbon" purpose. It provides an alternative to fossil fuels, and also offers novel approaches to environmental dilemmas such as global warming. Catalysts with an extensive specific surface area and plentiful surface active sites are capable of absorbing and aligning reactant molecules, including CO2 and methane, in an orientated manner. This reduces the energy required to activate the reaction, thereby enhancing the efficiency and selectivity of CO2 reduction and methane activation reactions. Developing novel catalysts with low cost, high catalytic activity, good long-term stability, and high product selectivity becomes popular to improve the efficiency of energy catalytic conversion. Perovskite composite oxides are a promising nanomaterial with superior redox performance, high stability, facile structural regulation, and rich active sites, offering some advantages for developed catalysts. For the advantageous properties of perovskite composite oxides in catalytic reactions, it is crucial to comprehensively investigate the catalytic mechanism of these oxides in CO2 reduction and methane activation, promote the development of high-performance perovskite composite oxide catalysts, and accelerate global efforts towards achieving carbon peak and carbon neutrality. Therefore, there is an urgent need to summarize the research progress on perovskite composite oxides for CO2 reduction and methane activation. This review represented the thermocatalytic, photocatalytic, electrocatalytic, and synergistic catalysis applications of perovskite composite oxides, with summarizing their catalytic performance in CO2 reduction and methane activation. Perovskite composite oxide catalysts have a potential in facilitating thermally catalyzed CO2 reduction and methane activation reactions. In particular, some rare-earth-based perovskite composite oxide catalysts serve a crucial function in this regard. The morphology, compositional structure, and surface adsorption properties of perovskite composite oxide catalysts are modulated via optimizing the preparation method and doping/substitution of metal elements. This leads to an increase in the oxygen vacancies and active sites of the catalysts, thereby improving their catalytic performance in thermocatalytic reactions. Compared to the photocatalytic and electrocatalytic materials, thermaocatalytic material yields a faster reaction rate, but the catalyst is susceptible to coking and carbon deposition at elevated temperatures. In addition, perovskite composite oxide catalysts demonstrate the superior effectiveness in the processes of photocatalytic reduction of CO2 and activation of methane. The energy band structure of the perovskite composite oxide photocatalyst are adjusted via doping with transition and rare-earth metals, optimizing morphology, regulating oxygen vacancy, loading cocatalysts, and constructing heterogeneous structures, etc.. This can broaden the light absorption range, reduce the reaction activation energy, promote the photogenerated carrier separation, inhibite the electron-hole pair recombination, and improve the reactant adsorption on the photocatalyst surface. This leads to the improved production rate, yield, and selectivity of the product. Photocatalysis offers environmentally friendly and controllable processes, yet it is limited due to its low reaction rate and selectivity for product formation. Also, perovskite composite oxide catalysts demonstrate a significant potential for electrocatalytic CO2 reduction and methane activation reactions. Perovskite composite oxides constitute a commendable class of electrocatalytic cathode materials showcasing exceptional ionic conductivity and redox properties. Scientists further enhance the conductivity of the materials by elemental doping at A/B sites and constructing oxygen vacancy to facilitate electron transfer, thereby improving the electrocatalytic performance of perovskite composite oxides. The electrocatalytic reaction offers some advantages like efficiency, cleanliness, and high product selectivity. Nonetheless, the reaction performance is extensively impacted underits reaction conditions (i.e., electrodes, electrolyte solution, etc.). In recent years, the combination of two or more catalytic technologies through synergistic catalysis has attracted much attention alongside the progress of catalytic research. Synergistic catalysis incorporates the benefits of individual catalytic technologies, while overcoming their inherent drawbacks, leading to the more effective and stable catalytic reactions. Synergistic catalytic techniques also allow catalysts that are not suitable for an individual catalytic reaction to be applied to a synergistic catalytic reaction under appropriate imposed conditions. Currently, perovskite composite oxide catalysts are still in their infancy for synergistic catalysis reactions, and researchers have not thoroughly examined the reaction conditions, basic principles, and interactions of various catalytic methods involved in synergistic catalysis reactions yet. The further exploration is required to generate more stable and efficient catalysts for synergistic catalysis reactions. Summary and prospects Perovskite composite oxides have some advantages of adjustable structure, excellent stability, and high catalytic activity, which make them a promising catalyst. They have undergone a significant growth since the initial simple CaTiO3, with dozens of varieties now available and in widespread use in energy conversion, chemical production, and environmental protection. This review represented recent research progress on catalytic CO2 reduction and methane activation by perovskite composite oxide catalysts. The objective was to offer a reference for research on perovskite composite oxide catalysts for catalytic energy conversion and related fields. In future research, we proposed the following perspectives: 1) new methods (e.g., high-pressure, high-temperature synthesis techniques and in-situ dipole source electrostatic field modulation strategies, etc.) and novelprocesses (e.g., supercritical fluid deposition and atomic layer deposition, etc.) are necessary to produce perovskite composite oxide catalysts with improved structural stability and diversity to enhance their performance; 2) The catalytic principles and reaction pathways of perovskite composite oxide catalysts are further investigated via theoretical calculations (e.g. first-principles calculations, molecular thermodynamics, and kinetic simulations, etc.) as well as characterization techniques (e.g. In-situ Fourier IR spectroscopy and in-situ electron paramagnetic/spin resonance, etc.) to provide a theoretical guidance for the design of perovskite composite oxide catalysts for a novel system; 3) The benefits of perovskite composite oxides should be maximized to extend their application in photothermocatalytic, photoelectrocatalytic, thermoelectrocatalytic, and photoelectrothermal synergistic catalytic as well.