Ablation failures of buffer layer in high voltage cross-linked polyethylene (XLPE) cables occur frequently,which has attracted widespread attention in the industry. The optimization of cable structure is conducive to solving the problem of discharge ablation. From the perspective of the discharge burn mechanism of buffer layer,the finite element model of cable is established for electric field simulation to analyze and discuss the variation of air gap electric field distribution under different structural parameters,thus designing and studying the structure optimization scheme. The results show that,on the premise of satisfying the design requirements of cable,it is beneficial to reduce the air gap electric field distortion because of poor contact,by reducing the thickness of the buffer layer and corrugated depth,as well as increasing extrusion depth between the metal sheath and the buffer layer. The smooth aluminum sleeve structure has low contact resistance with the buffer layer,so it has advantages in restraining fault of buffer layer discharge ablation.