Aiming at the problem of rapid and accurate transfer alignment for the space weapon strapdown inertial navigation system (SINS), the error model of weapon SINS was established and the errors of inertial elements were considered. The attitude matching was selected, and the measurement equation of the attitude error between space weapon SINS and satellite was deduced based on the principle of attitude transfer alignment. Based on these, the filter model of space weapon SINS was established and a rapid Kalman filter was designed for the space weapon-s transfer alignment. The results of simulation show that this model is efficient on filter-s convergence and precision. The alignment accuracy is similar to the one attitude measurement system of satellite have, and furthermore, the constant errors of gyros on space weapon can be calibrated.