Abstract: The research on equivalent frequency spectra of mechanical environment for satellite and launch vehicle is critical to the design of mechanical test conditions. In engineering practice, the equivalent frequency spectra of mechanical environmental parameters are usually obtained with the help of shock response spectrum transformation. However, this method has limitations that the equivalent frequency spectra change significantly with the steady-state amplification fator Q values. Therefore, a method for equivalent frequency spectral analysis of mechanical environment for satellite and launch vehicle based on short-time Fourier transform - adaptive optimal kernel (STFT-AOK) was presented. It is shown that STFT-AOK method can accurately locate the frequency and the time-frequency region of transient characteristics. In addition, combined with the accurate amplitude of STFT, the time-frequency distribution with high-resolution frequency and accurate amplitude was constructed to effictively obtain the frequency spectra of mechanical environment. The proposed research can be extended to the frequency spectral analysis of various complex transient mechanical environmental parameters for satellite and launch vehicle.