The emergence of the high-speed stealth targets severely compresses air defense missile radar seeker detection power, and especially limits linear frequency modulation waveform application in the process of terminal guidance, so that detection advantage on timefrequency two dimension high resolution is partly decreased. Aiming at this problem, a long time accumulation algorithm based on rotating and dimension reduction is proposed for pulsed Doppler radar seeker in order to detect the high-speed stealth target. The coupling between range and velocity in the echo matrix is wiped off by rotating transform, and the rotated matrix is independent in row and array respectively while the matrix dimension is reduced. The velocity between missile and target can be computed by Fourier transform, which is used to compensate the echo matrix. Through the simulation calculation, the seeker sensitivity is improved greatly.