A method of parameters estimation of spaceborne synthetic aperture radar based on combination algorithm of STFT and FRFT is proposed in this paper. Parameters here namely frequency centroid and frequency rate characterize the transmitted signal of spaceborne SAR. Estimation the parameters of the single way SAR signal is very important in ESM system. The combination algorithm of STFT and FRFT proposed in this paper overcomes the inaccuracy of direct estimation by STFT and large computation burden of pure FRFT. Simulation results show that this method is feasible and effective in improving the accuracy and reducing computational complexity for parameters estimation of spaceborne SAR.