Abstract: With the developing of ECM technology, airborne ECM systems have been a very important part of avionics in fight aircraft. Its efficiency evaluation has become a problem to which is paid much more attention by people.First of all, this paper discribes the function and position of ECM systems in modern air warfare and analyzes the importance of efficiency evaluation, then the method of operations research is used to analyze and calculate. The queuing system to be composed of attack aircrafts and air defence system is considered as a typical M/M/N queuing system. The penetration probability and survival probability is calculated by used of the queuing theory; There are two types of airborne ECM system, one is screen system, another is self protection system. The effect of ECM applications on the system efficiency is analyzed by means of game theory in those two cases. Finally, a method of calculation of the aircraft utilization factor is given by analyzing a combat process of EW.