With the vigorous development of space technology，space security has increasingly become a focal point in the field of spaceflight.The pursuit of on-orbit targets in space will also develop from the pursuit of single spacecraft to the trend of cooperative fencing by cluster spacecraft.This paper presents a strategy and method based on the state-dependent Riccati equation for the typical scenario of cluster spacecraft cooperative trapping of non-cooperative targets in space.First，based on the nonlinear relative motion model of spacecraft，a kinematic model of space cluster spacecraft cooperative trapping of noncooperative targets is established，and the quadratic objective functions （relative distance and fuel consumption） of both parties are designed accordingly，so that the trapping problem is transformed into a Nash equilibrium problem with differential countermeasures.Second，the state Riccati equation is solved，and thus the optimal strategy of cluster spacecraft against single non-cooperative target spacecraft is obtained.Third，with the null-space projection method，a distance-dependent priority-based mission planning scheme is designed to obtain the escape strategy of non-cooperative target spacecraft facing cluster spacecraft and to avoid the escape strategy conflict for the cluster spacecraft.Finally，numerical simulations are carried out，and the obtained results verify the effectiveness of the proposed cooperative fencing strategy and method.