Transformer crate of low-frequency power device has two transformers which are high-power device. A lot of heat is generated in runtime, lead to high temperature in transformer crate. It will reduce the reliability and stability of the transformer crate. This paper used Solidworks to build transformer crate model, and used Ansys to analyze the heat dissipation performance based on transformer crate model, besides long-term stability test for the transformer crate is conducted. According to the result of analyzed and tested, the heat dissipation performance optimization scheme is proposed and analyzed. At an ambient temperature of 25 °C, the maximum temperature in crate is 44.301°Cunder non-load operation and 66.676 °C under on-load, besides the maximum temperature is increased as the ambient temperature increased. The crate emitted more heat when it is on-load. The simulation error is 1.11% under non-load operation, 1.33% is under on-load. The result of simulation has great consistence with the actual working condition. After optimized the structure of crate, the average maximum temperature under different environment is reduced 8.97 °C. Therefore, the heat dispersion of crate is significantly increased and the operational reliability is also increased.