Abstract: In the radar and infrared(IR) sensor compound guidance under strong counterwork condition, intermittent working of radar can reduce the enemy missile interception probability and electronic support measures(ESM) lock probability. A radar/IR sequential filtering fusion algorithm was proposed in radar/IR compound guidance with radar under intermittent-working state. The algorithm used sequential centralized multisensor fusion method for target tracking considering that the measurement of radar and infrared sensor was non-synchronous. Sequential filtering fusion algorithm based on interacting multiple model and extended Kalman filter(IMM-EKF) was used for target tracking. The algorithm used the comparison of the state estimation covariance and the measurement error variance to control radar under intermittent-working state. The algorithm can automatically adapt to radar under intermittent-working state, need not switch over single sensor tracking mode and dual sensor tracking mode. The influence of the sensors data rate and radar under intermittent-working state on radar/IR compound tracking precision was analyzed.