In the process of the terminal guidance of a kinetic kill vehicle (KKV),it is very important to accurately estimate the line-of-sight (LOS) rate via the measurements of a target seeker on-board the KKV.The strong impact interference caused by the large lateral thrust produced by the thrusters on the KKV is a main factor that affects the measurements on the LOS angle.A method to estimate the impact interference and the LOS rate to-gether via a Kalman filter is proposed to improve the estimation precision of the LOS rate.The observability of the system de-scribing the missile-target relative motion model and the impact interference model is proved,and then a Kalman filter is de-signed.In the Kalman filter design,the continuous-discrete and two-stage filtering techniques are used because the system model is time-variant and high-order.Numerical simulation re-sults show that by estimating the impact interference,the esti-mation precision of the LOS rate is increased,and so the miss distance of the KKV under the strong impact interference is re-duced.The proposed continuous-discrete two-stage Kalman fil-ter shows higher estimation precision and lower computational cost than the naive discrete augmented state Kalman filter.