In this article, we discuss the dynamics characteristics of contact and impact when the hand of space manipulator captures the free-flying target (FFT). We establish the dynamics model of contact and impact between a space manipulator and FFT. The pre-impact, post-impact effect and condition of the space robot system and the FFT system are analyzed when there are any differences between the speed of the end-effector of the space manipulator and that of the contact and impact point on the surface of FFT. We present the relationship between the speed varieties of the space base and that of the FFT. If the impact force is kept constant, the speed varieties of the space base are different when the space robot system is at different configuration. Those methods can be used to analyze the contact and impact problem of the space robot.