The structural design of airborne electronic equipment should meet the fatigue life requirements under long-time random vibration. The finite element simulation method can accurately predict the fatigue life distribution of the structure in the vibration environment, and optimize the weak areas of the structure, which can effectively improve the success rate of the first design. In this paper, based on the frequency domain fatigue analysis method, combined with Miner's linear cumulative damage theory and material S- N curve, the fatigue life analysis of an airborne power supply unit under random vibration is carried out, and the results are in good agreement with the test. The fatigue failure mechanism is analyzed, and the structure is optimized, which effectively improves the fatigue failure resistance of the structure.