Abstract: In order to accurately estimate the line-of-sight (LOS) angular rate of the strapdown seeker, strapdown seeker mathematical model was established, decoupling and estimation algorithm of LOS angular rate was based on the movement of the missile and target relative relationship. Firstly, a mathematical model of the strapdown seeker was established, and the Taylor series was used for its linearization. Secondly, according to the movement of the missile and target geometry and coordinate system relative relationship, the LOS angular rate decoupling algorithm was derived. Strapdown seeker can not directly measure the body line-of-sight (BLOS) angular rate, differential coefficient+steady-state Kalman filter was proposed to estimate the BLOS angular rate. Finally, LOS angular rate decoupling and estimation algorithm verification system was established and simulation experiment was carried out. The results showed that, the absolute error of decoupling algorithm was less than 510-5 rad/s and relative error was less than 0.3%, the correctness of the decoupling algorithm was verified. Under the conditions of containing seeker mathematical model, the steady-state Kalman filter was used by the angular frequency of 19.2 rad/s, LOS angular rate estimation error was less than 410-3 rad/s, nearly an order of magnitude was improved than direct differentiation method estimation error. The decoupling and estimation algorithm of the LOS angular rate can at the same time meet the requirements of the guidance system accuracy and dynamic performance.