Abstract: When the range-Doppler algorithm is used in inverse synthetic aperture radar (ISAR) imaging, the reduction of echo correlation will add more difficulties on motion compensation and bring more error. Accordingly, based on the adjacent-correlate compensate method used in FFT range-Doppler algorithm, an improved compensation method is presented in this paper. The traditional compensation method is modified to avoid the envelope drift and envelope jump in range align. In phase compensation, a new algorithm based on accurate target parameter estimation by use of discrete chirp-Fourier transform (DCFT) transform is presented. Finally the improve method is verified by simulation.