To reduce the pressure of data processing, the dechirp operation is adopted. However, dechirp will result in range-dependent phase errors in the beat signal. an algorithm to compensate the range-dependent phase error is proposed, using the phase error extracted from the transmitted signal with the supposition that the phase error varies slowly. The compensation approach is executed in two steps: first, compensating the phase error involved by the transmitted signal after dechirp; second, compensating the residual phase error after RVP correction. Both the simulation and the real data experiments suggest that the proposed algorithm is effective.