In recent years. With the modernization of the war on missile of low cost and minute extension requirements are constantly strengthened, the strap-down seeker guidance system is becoming a developing trend. However, the measuring system of the strap-down seeker is fixed to the projectile body compared with the traditional platform seeker. During the flight of the missile, we can’t obtain the sight angle velocity of missile in inertial space because of the coupling effect. A method of decoupling and filtering of missile guidance information for strap-down seeker in this paper. The effective guidance information for proportional guidance of missile is calculated. Then Carry out the numerical simulation and target accuracy statistics. Simulation results show that this method can accurately isolate the influence of missile attitude on the guidance information and hit the target accurately. This paper provides an effective reference for the engineering application of the strap-down seeker system.