Ethylene selective oligomerization as a key technology for preparing 1-hexene and 1-octene, holds an important position in the field of advanced polyolefin materials and fine chemicals. Catalytic systems based on PCCP ligands have attracted substantial interest due to their exceptional catalytic performance and tunable product distribution. This review provided a comprehensive summary of various PCCP ligands under diverse reaction conditions. By comparing experimental results, the influences of temperature and pressure on the oligomerization process were elucidated. Furthermore, the regulatory effects of steric and electronic properties—originating from substituents on the phosphorus atoms and the carbon bridge—on the catalytic activity and selectivity were discussed in detail. Finally, the integration of density functional theory (DFT) and machine learning in mechanistic studies and high-performance ligand screening was introduced, followed by an outlook on future directions for advancing ethylene selective oligomerization technologies.