Abstract: Tether-nets are currently the most promising method for active space debris removal; however, the dynamic simulation process of debris capture is often computationally difficult. The collision between the tether-net and the debris, and the self-collision of various parts of the net, are the key issues in the dynamic modeling of space debris capture. The lumped parameter method is used to model the tether-net system, and a line-line collision model is proposed to describe the self-contact of the net, and the collision between the tether-net and the debris is regarded as a combination of point-surface collision and line-line collision, which can quickly establish the dynamic model of the capture process. The numerical example shows that the penetration of the net and debris can be prevented while effectively capturing space debris. This method can provide numerical reference for the initial design of tether-net.