Various defects caused by aging in cable structures have led to frequent faults in high-voltage XLPE cables, which has attracted widespread attention in the industry. In order to explore the gas generation law of semi conductive layer defects in cables, a finite element simulation model of 110 kV cables was constructed. The gas generation process of defects in cable conductor shielding layer and insulation shielding layer was simulated. And make concentration measurement points for each structure of the cable to compare the diffusion patterns of gases in different structures. The simulation results show that: (1) under the same other conditions, the gas production from the insulation shielding layer defect is more easily detected. (2) Under the gas production of defects in the conductor shielding layer and insulation shielding layer, excluding the cable structure where the defect is located, the conductor and buffer layer are the areas with the highest concentration, respectively. Therefore, it is recommended to use the conductor and buffer layer as suitable measurement points for gas production in two types of semi conductive layer defects.