Abstract: Coherent decoy technology can induce ARM outside the area of radiant sources compared with the noncoherent decoy technology widely used now， it has great importance in practicality， but the choke point of utility is the accurate control of phase difference of radiant sources. The model of two radiant sources decoying ARM is built in this paper， relationships between phase difference and the factors of radiant sources and ARM is analyzed， and phase difference needed under coherent safe decoy is deduced. Combined with the movement model of ARM， a data processing method —VD-Kalman filter is proposed to improve the location precision of ARM， decrease the phase difference error. Simulation results demonstrate the effectiveness of the method.