The characteristics of echo and imaging of Doppler beaming sharpening during the missile's descending flight were discussed. According to the built geometric model, target range expressions were deducted, and the features of range variation with time and Doppler parameter variation with operation time were analyzed, and then the key parameters were also described. In the paper, an algorithm FFT with a constant pulse repeat frequency was adopted and the imaging was simulated. Due to the attitude of missile decreasing during the whole time, geometry distortion existed in the imaging.