As one of the failure forms of structure, vibration fatigue is getting more and more attention. However, the traditional design of shipborne radar only considers the static strength, which leads to the lack of the ability to resist fatigue damage. From the perspective of modal analysis, this paper uses modal superposition method for random vibration analysis, so as to obtain the power spectral density of structural stress in all directions. On this basis, the spectrum analysis based on Von Mises stress is carried out, and the fatigue life is estimated from the perspective of broadband and narrowband processes respectively. Finally, the random vibration fatigue analysis of a shipborne radar is carried out. The results show that the structure of shipborne radar can not meet the requirements of anti fatigue performance under the condition of static strength. Then, from the perspective of modal analysis, the structural design is improved. Finally, through the analysis, it is concluded that the improved structure can meet the requirements of random vibration fatigue life.