Aiming at the motion features of high speed moving target in space, by analyzing the range migration trajectory (RMT) and the equivalent motion model of the target, a RMT-based joint motion compensation algorithm is proposed in this paper. In the algorithm, the translational parameters of the target are estimated from RMT according to the global entropy minimization principle. Then the range profile offset is compensated and one dimensional range alignment distortion is corrected by using these translational parameters, which can realize the joint motion compensation of range alignment and intra pulse moving for the space target echo. Simulational and experimental results show that the proposed algorithm has high accuracy. What's more, ransom offset error and phase error cannot be introduced in the range alignment procedure, which is the precondition of high-resolution imaging method application.