The strapdown phased array radar seeker is directly fixed to the missile body and can only provide the target's body line of sight angle for the guidance system. Therefore, when the terminal guidance ammunition adopts the traditional proportional guidance and applies the strapdown phased array radar seeker, it also needs to extract the line of sight angle rate combined with the missile body attitude information to form the terminal guidance command. In order to solve this problem, based on the information provided by the seeker, such as the target's body line of sight angle, the relative distance between the missile and the target, the relative approach speed, a technique for estimating the line of sight angle rate of the strapdown phased array radar seeker is proposed using adaptive unscented Kalman filter. The simulation results show that the proposed algorithm has better estimation effect on the line of sight angle rate than the aẞ filter commonly used in engineering, and has higher hit accuracy; the embedded implementation of the algorithm based on a highperformance microprocessor shows that the single run time of the algorithm is longer than that of the aẞ differential filter, but it still meets the realtime requirements in engineering.