Abstract: As one of high-resolution radars, millimeter wave stepped frequency waveforms radar is successfully and widely used in many military applications. Main factors affecting the performance of radar are analyzed. Apart from target velocity, the dispersion of frequency synthesizer providing signals to radar also deteriorates the performance of radar. Specifically speaking, the dispersion in microwave band will be transferred to millimeter-wave band, this will result in the fact that the initial phase difference between transmitter and local oscillator is not constant, and brings bad impact on the resolution of radar. In order to ameliorate such effect, one possible way is to compensate dispersion. In this paper, an effective way to compensate dispersion is successfully applied in the design of a W-band stepped frequency waveforms radar. The final experiment shows that it can meet the requirement of 0.45 m range resolution.