Abstract: In order to investigate the stabilization of optical axis of semi-strapdown seeker, the factors that influence the stabilization were analyzed. The essence of semi-strapdown stabilization was proposed by comparing with the traditional gyro stabilization method. The expression of the inertia-space velocity of optical axis was showed, and the main factors that influence the semi-strapdown stabilization were analyzed. The matched filter and disturbance obverse were used to improve the precision of semi-strapdown stabilization against missile disturbance and disturbance torque. The numerical simulation result shows that the matched filter rises 38 dB of the coupling precision at 1 Hz; the influence to stabilization caused by disturbance torque is greatly reduced by disturbance observer; and the stabilization error caused by velocity measurement is improved by using high precision and low noise sensor. The integrated simulation result shows that the stabilization error is declined nearly 94 percent after compensating for the three main factors.