The problem of discriminating active decoys and radar target was studied based on the radar data processing in the background of missile defense. On the basis of the essential difference of the dynamic model between those active decoys and the real target, the concept of dynamic model match coefficient was proposed. The analytic expression of the coefficient was presented without considering the radar measurement noise. The discrimination threshold was designed based on the radar tracking data. The computer simulation was carried out with the background of an intermediate range ballistic trajectory. The feasibility and validity of the proposed algorithm was verified by the simulation results.