Abstract: With the continuous advancement of the construction of new power systems, in the environment of high altitude, high salt spray and high temperature. The miniaturization of switchgear and the demand for high current are increasing year by year, but the temperature rise caused by high current poses new technical challenges to the heat dissipation of epoxy resin. The thermal conductivity of ordinary epoxy resin limits the application of high-current switches, and there is an urgent need for new materials and processes to develop new epoxy resin heat dissipation materials to solve the problem of high-current heat dissipation. This article describes the preparation of different proportions of alumina filler in epoxy resin. The thermal conductivity and electrical properties of the composite material were measured. Its thermal conductivity reaches 3 W/（m·k）, and its electrical performance is higher than the industry standard. The application technology of micro-Al₂O₃ epoxy resin in shielded solid fully insulated switchgear is realized.