Electronic instrument transformers are usually used in combination with gas-insulated switchgear in power systems under harsh conditions. When current flows through the high-voltage conductor in the electronic instrument transformer, it will cause the equipment to heat up, which in turn affects the reliable operation of the equipment. This paper comprehensively considers electromagnetic heat and the heat transfer characteristics of solids and fluids, establishes a multi-physics coupling simulation model of the electronic instrument transformer based on COMSOL, and performs a laminar flow analysis on sulfur hexafluoride installed in the electronic instrument transformer segment. By analyzing the internal temperature distribution, the velocity of SF6 gas, the y component of the velocity field inside the equipment, the internal pressure contours, and the magnetic flux density distribution, the compatibility of the electronic instrument transformer and the gas-insulated switch combination is evaluated, and compared with the theoretical analysis results. The multi-physics coupling simulation model proposed in this study has good accuracy and lays a theoretical foundation for experimental testing and optimization design related to electronic instrument transformers.