Capturing the target successfully is the key to accomplish the on-orbit service task such as space station assembling, satellite maintenance and refueling in the future. The end effector based on the wire rope has the properties of big tolerance and soft capturing, so it has a definite advantage to capture the spacecraft which is of large inertia and high speed. In this paper, we build the dynamics model of the rope using the 6 dimension spring flexible connection based on the discretization method, introduce the contact force between the rope and the target to obtain the capturing dynamic model of the end effector. This model fully considers the process of contact-impact between the wire rope and the target. Because having the ability to predict and prevent the impact brought by the capturing process, it is not only a meaningful explore in designing of mechanism and controller, but also an effective supplement for the physical experiment to solve the problem that it is difficult to do the ground test of the space large target capturing task for China in the future.