The missile radar seeker in reentry section was taken as the research object for studying the point target echo model of it in the reentry high-speed flight mode.Based on the principle of Delaunay triangulation, the digital elevation terrain was divided into a number of triangular scatter grids by the interpolation algorithm of Lawson.After that, the altimeter echo model of the single pulse chirp signal radar under complex terrain in the reentry section of missile was established by using the principle of power superposition.And the rough surface average impulse response model proposed by BROWN was used to carry out simulation under the same condition, which verified the applicability of the echo model proposed in this paper.