Abstract: Motion parameter estimation method based on time-frequency analysis is proposed to overcome the influence of the target movement on its image in frequency-stepped chirp signal radar system.By taking the Fourier transform for the echo after dechirp firstly, based on the linear frequency modulation of the subpulses sequence, the motion parameter at every time can be estimated by the method which is combined by Wigner-Ville distribution (WVD) and Radon transform.Then, the binary mathematical morphology and edge detection method is used to improve the accuracy of the velocity estimation of the target which contains many scatterers.Finally, the least-square algorithm is used to obtain the motion parameters with better accuracy when the maneuvering target velocity varied within the imaging time. Simulation verifies the validity of motion parameter estimation method proposed in this paper.