Abstract: The operational effectiveness of antagonizing ARM using multiple fake targets to protect a true one was investigated. Having established the aiming direction of an ARM, a method of computing the capture probability of the true and the fake targets was presented when seeker differentiates targets. A universal formula for computing killed probability of the true targets under the attacks of ARM time after time was educed. The results show that the influence of accumulation of targets loss must be considered when evaluating operational effectiveness for fake targets antagonizing ARM and their vulnerability should be reduced, their eradiation power should be improved, and reasonable configuration should be adopted when the number of fake targets is increased to improve the operational effectiveness.