Abstract: It is very difficult to specify appropriate random vibration test inputs for spacecraft components, which are usually given in terms of test results or experiences. In this paper, a new technique based on the hybrid FE-SEA method is applied to the prediction of the random vibration environment, and the random vibration as specified by the predictive results is studied. Firstly, the formulation of the hybrid FE-SEA method is briefly discussed. Then, the acceleration power spectral densities for components are computed by the FE-SEA method under the combined loads of the external acoustic loads and the direct mechanical vibration inputs from the interface between the launch vehicle and the spacecraft. Finally, an approach is proposed to specify random vibration test inputs for components in consideration of the predictive results and the technical inspection requirements. It is concluded that FE-SEA is efficient in the modeling work, is especially suitable for the prediction of component responses under combined loads, and is convenient to be applied in specifying the random vibration inputs.