Abstract: Evaluation problem of formation fighter’s beyond visual range interception effectiveness was studied by Lanchester theory. Comparing hypothesis condition of Lanchester theory with actual background of beyond visual range interception, detection and attack phases of interception mission were respectively described by secondary linear law and square law. On the principle of maximum commutative loss ratio, fire distribution was introduced into evaluation model. Dynamic models of detection effectiveness and attack effectiveness were established by using finding probability of airborne radar and hit probability of air-to-air missile respectively. A numerical example shows that value coefficient of assault side-s escort fighter significantly influences fire distribution of interception side, and interception side-s tactics selection attacks escort fighter first and then fighter bomber. Interception effectiveness could be improved both by using electronic countermeasure and enhancing fighter survivability, and the model is not only an easy calculation but also reasonable and effective.