Abstract: According to the coherent phase-coded pulse train (CPCPT) signals used in terminal radar seeker, a long-term coherent integration method is proposed. Without requiring any accurate velocity information, Keystone transformation is used for range migration compensation. Fourier transform is carried out for the coherent integration. In order to reduce the computation complexity, DFT-IFFT algorithm is used for the implementation of Keystone transformation. In support of the method, CPCPT maintains the coherent integration gain and the resolution in range and Doppler without the range-Doppler coupling. Some computer simulation results are presented which illustrate the effectivity of the method.