The method of towing space debris using space tether system (STS) has become an important non-contact approach for space debris removal in recent years. However, there is still a relative lack of research on the towing of large non-cooperative targets using STS, and the existing mathematical models are insufficient for describing the motion of the entire system during the towing process. This paper takes the scenario of a small STS towing a rocket debris as an example and proposes a novel “particle-rigid body-spring” configuration mathematical model, which effectively represent the system’s motion behavior. By applying the second kind of Lagrangian equation for dynamic modeling, the corresponding Lagrangian function and the equations of motion for each generalized coordinate are derived. Based on this, the process control for reducing the orbital altitude of the towing space debris is investigated. A numerical solution to the system’s differential equations under given towing conditions is: provided, and a corresponding control method is designed to ensure the steady progression of the towing process.