Abstract: To address the capacity degradation, voltage fading, structural instability and adverse interface reactions in cathode materials of lithium-ion batteries (LIBs), numerous modification strategies have been developed, mainly including coating and doping. In particular, the important strategy of doping (surface doping and bulk doping) has been considered an effective strategy to modulate the crystal lattice structure of cathode materials. However, special insights into the mechanisms and effectiveness of the doping strategy, especially comparisons between surface doping and bulk doping in cathode materials, are still lacking. In this review, recent significant progress in surface doping and bulk doping strategies is demonstrated in detail by focusing on their inherent differences as well as effects on the structural stability, lithium-ion (Li-ion) diffusion and electrochemical properties of cathode materials from the following mechanistic insights: preventing the exposure of reactive Ni on the surface, stabilizing the Li slabs, mitigating the migration of transition metal (TM) ions, alleviating undesired structural transformations and adverse interface issues, enlarging the Li interslab spacing, forming three-dimensional (3D) Li-ion diffusion channels, and providing more active sites for the charge-transfer process. Moreover, insights into the correlation between the mechanisms of hybrid surface engineering strategies (doping and coating) and their influences on the electrochemical performance of cathode materials are provided by emphasizing the stabilization of the Li slabs, the enhancement of the surface chemical stability, and the alleviation of TM ion migration. Furthermore, the existing challenges and future perspectives in this promising field are indicated.