Missile-borne step frequency MMW radar can get high resolution range profile, b u t when moving target has radial velocity relative to the radar, it makes the echo signal produce serious deviation and distortion, so it is necessary to mak e compensation in the motion velocity. Firstly, this paper analyzes the image fo rmin g principle of missile-borne step frequency MMW radar and the effect of the tar get v elocity on image forming, then discusses the quadratic velocity estimation algo rithm, which is on the basis of the positive and negative frequency modulation m ethod and the maximum pulse group summation method. It provides a parallel imple mentation scheme of the algorithm on the TMS320C6678 multi core DSP platform, a n d describes the implementation scheme of task allocation, scheduling and inter c ore communication process at the same time. Finally it carries out an algorithm test to 1 000 frames echo signal on multi-core DSP platform, whose result shows t hat the motion compensation algorithm has high accuracy and good real-time perf ormance based on multicore DSP.