Large roll disturbance occurs while the missile is maneuvering, azimuth-elevation two axis stabilization system is widely used in radar seekers, research on how LOS (line of sight) rate output of radar seeker is affected by roll disturbance is a valuable topic in radar seeker design. In this paper, the roll disturbance of missile is researched through platform axis' error differential analysis combine with semi hardware in loop simulation, which shows that roll disturbance is isolated through two axis stabilization system, however, the direction error between electric axis and platform direction results in LOS rate errors related to missile roll disturbance.