The composite nanostructures composed of different semiconductors endow them with the high separation rate of photogenerated electrons and holes through the charge transfer effect at the heterojunction interface, to achieve high performances of the photocatalysts. Based on such nanostructure, multiple nano-heterostructure photocatalysts has become a research hotspot in the field of photocatalysis. Among them, ZnO/TiO₂ nanocomposite material exhibits excellent photocatalytic performances, while the existing synthesis process is complex and limits its industrial application in photocatalysis. For this reason, based on the modified polymer network gel method, we prepared a highly efficient ZnO/TiO₂ nanocomposite photocatalyst by the simply designed process routes, and adjusted the ratio of the components in the composites to optimize the photocatalytic performance. The TiO₂ content was calculated according to the molar ratio of Ti/(Ti + Zn), which are 0.2 mol/mol, 2 mol/mol, 10 mol/mol, 25 mol/mol and 50 mol/mol respectively. The corresponding samples were labeled as ZT0.002, ZT0.02, ZT0.1, ZT0.25 and ZT0.5. The phase compositions, morphology features, microstructures, surface chemical states, and optical and electrical properties of the catalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, inductively coupled plasma mass spectrum, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectrum, ultraviolet and visible spectrophotometry and steady-state surface photovoltage spectra. Also, we studied the photocatalytic degradation characteristics of the catalysts toward methylene blue and methyl orange under simulated sunlight irradiation. Correspondingly, the mechanism about the change in the composition of the composite photocatalyst causing the change in its catalytic activity was proposed.The results of the study indicated that the addition of a small amount of TiO₂ and compositing with the high-concentration TiO₂ both improved the catalytic activity of the granular ZnO nanophotocatalyst. Under simulated sunlight irradiation, they possess the higher degradation efficiencies to methyl orange, and the enhanced performances are respectively attributed to the enhanced charge carrier separation efficiencies caused by the increased surface oxygen vacancy defects and the enhanced interfacial charge transfer in the multi-heterojunction structure. To be specific, the phase composition and microstructure analysis indicated that the only hexagonal wurtzite phase ZnO is observed in ZT0.002, while there is a multi-heterojunction structure composed of hexagonal wurtzite phase ZnO, anatase phase TiO₂ and cubic phase Zn₂TiO₄ for the samples composited with the high-concentration TiO₂. The morphology feature analysis indicated that ZT0.002 and ZT0.5 exhibit less particle agglomeration, uniform particle size distribution and larger average particle size compared with other samples. Although the large average particle size results in a small specific surface area, less particle agglomeration reduces the recombination of electrons and holes migrating to the interfaces between the crystals. The surface chemical state and defect situation analysis indicated that ZT0.002 has a higher concentration of surface oxygen vacancy defects than that of ZnO, which is caused by the regulation of the nucleation, crystallization and crystal growth process of ZnO by a trace amount of TiO₂. The increased surface oxygen vacancies promote the separation of photogenerated carriers and increase the active adsorption sites for the reactant molecules. Likewise, the photogenerated carrier separation efficiency is enhanced by the formation of the multi-heterojunction structure among ZnO, TiO₂ and Zn₂TiO₄.In addition, ZnO and TiO₂ showed a certain selectivity for the photocatalytic degradation of methylene blue and methyl orange, which is related to the electrification of the catalyst surface and the ionicity of pollutant molecules. Radical scavenger experiments showed that the surface active species such as hydroxyl radicals and superoxide radical as well as photogenerated holes participate in the degradation reactions of methylene blue and methyl orange on the catalyst surfaces, and superoxide radical plays a dominant role in the degradation of methyl orange. Cycling experiments evidenced the high stability of the as-prepared photocatalyst. For practical applications, the influences of the catalyst dosage and pH value of the pollutant solution on the photocatalytic performance of the catalyst have also been studied.