Aimed at the problems that an early warning aircraft is limited in maneuverability and is also subject to the “targeting dagger” threat of enemy advanced missiles in air combat, an active defense method is designed. First, an early warning aircraft or escort aircraft is to launch one or more defense missiles to combat incoming missiles. Second, the early warning aircraft is to evade them under condition of battlefield perception, information sharing and tactical coordination. Based on the research of the optimal cooperative guidance algorithm with the optimal control theory in the threebody attack and defense confrontation problem composed of target aircraft, defensive missiles and target missiles under the twodimensional plane, the cooperative guidance law is extended from twodimensional to threedimensional through twodimensional projection method for active defense process in threedimensional space which transforms the design problem of the threedimensional active defense guidance law into two mutually constrained twodimensional plane guidance law (horizontal and vertical plane) design problems. The simulation results show that the proposed guidance algorithm can effectively intercept the incoming missiles under different attack modes in space and meet the needs of interception accuracy. The simulation results show that compared with the traditional interception guidance algorithm, the proposed guidance algorithm not only meets the required interception accuracy, but also has a smaller interception overload and has certain advantages.