Focusing on the applicability of the frequency domain method and time domain method in random vibration fatigue calculation， the accuracy and efficiency of the two methods are comprehensively studied with a certain type of battery pack as the research object. First， a finite element model of the battery pack is established and verified through the modal test. Secondly， the acceleration Power Spectral Density （PSD）of GB 38031―2020 is taken as the load spectrum in the frequency domain and converted into the time domain load using Fourier inverse transformation technology. Finally， the vibration acceleration， stress， and fatigue life of the battery pack are calculated based on the frequency domain method and the time domain method， respectively. The calculation accuracy and efficiency of both methods are compared and verified by the test. The results show that in regard of the total vibration level and stress RMS value of the battery pack， the calculated values of the frequency domain method and the time domain method are similar， and the relative error is less than 16%. For the peak value of acceleration and stress， the "3σ" calculation results of frequency domain method are much different from those of time domain method. With the adoption of the "4σ" or "5σ" principle， the calculation results of both methods are similar， and the relative error is less than 15%. In concern of vibration fatigue， the calculated life by the frequency domain method is about as 3 to 6 times long as that by the time domain method. The main reasons include Dirlik model and stress response PSD， in which the difference caused by the Dirlik model is less than 1.5 times. In terms of computational efficiency， the frequency domain method is about 134 times faster than the time domain method. The test data show that the time domain method is with higher accuracy and suitable for the accurate calculation of vibration fatigue at dangerous positions， while the frequency domain method is more efficient and suitable for the rapid prediction of structural high-risk positions.