It is of great significance to add an insulation layer to the enclosure structure of the prefabricated cabin substation to enhance the thermal insulation and energy-saving performance of the prefabricated cabin, improve the thermal environment in the cabin, ensure the safe and stable operation of the electrical equipment in the cabin, and realize energy saving, emission reduction and green and low-carbon. In this paper, the steady-state heat conduction equation of the prefabricated cabin of the substation with basalt fiber composite prefabricated parts as the enclosure structure is established by using the principle of steady-state heat conduction of the flat wall, and the operating energy consumption cost generated during the use of the equipment is analyzed by using the LCC life cycle cost method, and the calculation model of the optimal insulation thickness of the whole life cycle of the envelope structure of the prefabricated cabin substation is established, and the optimal economic thickness of the insulation layer of the prefabricated cabin substation is calculated through the actual engineering case. It provides a valuable reference for the design of insulation thickness for similar prefabricated cabin electrical equipment.