This paper presents a discrete cooperative pursuitevasion strategy when a high value vehicle or a evader launches a defender as a countermeasure against an incoming enemy interceptor. This paper utilizes a linear quadratic differential game formulation for analyzing arbitraryorder linear players dynamics, and gives out the optimum solutions for discrete quadratic performance index. The paper takes into the consideration of the game composed of two agents, i.e. the optimal cooperative evasion strategy for the evader, the optimal cooperative pursuit strategy for the defender, and the optimal strategy of the homing interceptor for pursuing the evader and for evading the defender. The obtained guidance laws are dependent on the zeroeffort miss distances of two pursuerevader pairs: interceptor with the evader and defender with homing interceptor. The simulation results are used to validate the defensive effect under cooperation. The advantages of cooperation are shown. Compared with the conventional oneonone guidance law, the cooperation greatly reduces the maneuverable requirements from the defending missile. The simulation also shows that the algorithm is good in robustness to the uncertainty of weight.