Abstract: In dynamic parameter identification of on-orbit spacecraft,the modal frequencies are low and high density,the excitation sources are limited and indiscernible.According to these characteristics,a dynamic parameter identification method for on-orbit spacecraft was investigated,directly utilizing on-orbit response to identify the dynamic parameters in frequency domain.It can be used for low and high density frequency identification without excitation information.Considering the characteristic of low and high density frequencies,a simulation test system for dynamic parameter identification of on-orbit spacecraft was developed,which was used to validate the method above.