Structural fatigue damage, especially random vibration fatigue in the frequency range between high and low cycle is more worthy of attention. The life prediction of the structure is significant. The frequency domain analysis based on the power spectral density function (PSD) was chosen to perform structural fatigue life analysis. The PSD function of the stress response at the structural critical positions was obtained by the finite element analysis. It was used to estimate the fatigue life using the classical cumulative damage rule and material characteristics. Different stress distribution models with different severity were investigated. A chosen case study of beam structure was performed to verify the reliability of the simulation in both stress response and failure time according to experimental tests. Finally, a life prediction of beam structures could be obtained using random vibration testing simulation.