With the development of electronic countermeasure technology, the requirements on anti-jamming ability, resolution of radar become stricter than before. In this paper, a kind of sidelobe suppression filter is designed for random hopped-frequency wide-band radar. Taking the high price of instantaneous bandwidth signal and weak anti-interference into consideration, a discrete random step- frequency signal is adopted. According to the signal characteristics and on the basis of predecessors, a filter design is proposed for the signal. The simulation results show that the designed filter can suppress the sidelobe obviously, with the characteristics of lower peak sidelobe and easy to be realized, which improves the performance of wide-band radar.