All inorganic perovskite nanocrystals of CsPbX3 (X=Cl, Br, I) have superior properties such as high fluorescence quantum yield, narrow half-peak width and easy adjustment of emission wavelength, etc., which have wide application prospects in light-emitting diodes, solar cells and photodetectors. However, CsPbX3 nanocrystals have a poor stability under light, moisture and heating conditions due to their ionic properties, restricting their practical application. Metal ion doping can affect the electronic band structure of CsPbX3 nanocrystals, thus effectively improving their photoluminescence properties. The doped metal ions can be divided into main group metal ion, rare-earth metal ion and transition metal ion. Transition metal ion has a lower price, and it can efficiently improve the stability of perovskite nanocrystals. This review represented recent work on the effect of transition metal ions (i.e., Mn2+, Ni2+, Cu2+, Zn2+, etc.) doping on the properties of perovskite nanocrystals. In addition, the challenges in the development of doped all-inorganic perovskite nanocrystals were analyzed, and the future development direction was also prospected.Transition metal ion doping CsPbX3 nanocrystals (NCs) are explored extensively. Mn2+ doping can improve the formation energy of CsPbX3 NCs with a high stability. Mn2+ doping exists in wide-band-gap perovskite hosts where the excitation energy is transferred to Mn d-state, resulting in short-range tunable yellow-orange d-d emissions. Low concentration Mn2+ doping is beneficial to enhancing the exciton emission, and the Mn2+-doping sample has a long PL lifetime. Ni2+ doping can eliminate the structural defects of CsPbX3 NCs, resulting in the improvement of the lattice order. Compared with the undoped sample, doping Ni2+ also induces the formation energy of CsPbX3 NCs and triggers the phase transition of CsPbBr3 from orthorhombic to cubic, which is attributed to the lattice strain due to the size mismatch of Ni2+ and Pb2+. Ni2+ doping reduces the non-radiative recombination efficiency and increases the fluorescence intensity of the CsPbX3 NCs. Cu2+ doping sample maintains a cubic crystal structure of the initial phase. When Cu2+ with the smaller radius (i.e., 0.72 ?) replaces Pb2+ ion with the larger radius (i.e., 1.19 ?), the shrinkage of lattice contraction regulates the tolerance factor of the [PbBr6]4- octahedron, and increases the lattice formation energy, resulting in high stability and fluorescence intensity of NCs. Compared with Pb2+ (i.e., 1.19 ?), Zn2+ has smaller ion radius (i.e., 0.74 ?) and a lower toxicity. The introduction of Zn2+ can effectively passivate the surface and internal defects of CsPbX3 NCs. Doping Co2+ can increase the formation energy, improve the short-range order of the lattice, and enhance the different monochromatic band edge emission without introducing new composite channels. Doping Cr3+ can regulate the structure and the optical properties of NCs. Doping Fe2+/Fe3+ has some advantages like low cost, high electrical conductivity and magnetic properties. Moreover, an appropriate amount of Fe2+ doping improves the size uniformity of CsPbX3 NCs, as well as increases the PLQY and the average PL lifetime due to the decrease of the defect state and nonradiation recombination of NCs. Furthermore, the application of transition metal ion doped CsPbX3 NCs in white light-emitting diode (WLED), solar cells and laser devices was outlined. The employment of doping transition metal ions into perovskites can improve the optical properties and stability, which energetically facilitate their applications. Finally, the main future research directions of transition metal ion doped CsPbX3 NCs were concluded.Summary and prospects Transition metal doping can promote the radiative recombination of excitons, and the defect formation energies of VCs, VBr and VPb are effectively improved, resulting in an improvement of the luminescence performance of CsPbX3 NCs. However, some problems need to be solved in the future. The PL linewidth of nanocrystals for the application of bioluminescence imaging and LED fields needs to be reduced. The external quantum efficiency (EQE) and luminous efficacy (LE) of transition metal doped CsPbX3 NCs still need to be improved, compared to that of Cd-based QDs. Finally, there are still potential risks associated with the reaction, and the PLQY still needs to be further improved. The investigation of transition metal ion doping all-inorganic CsPbX3 NCs has a profound impact on the scientific research and commercial applications of fluorescent materials.