Abstract: The time synchronization is the key issue of wideband distributed coherent aperture radar. However, current time synchronization technology could not meet the requirement of high accuracy of time synchronization for wideband distributed coherent aperture radar. In this paper, a time synchronization method based on step frequency signal was proposed. Firstly, the impact of time synchronization error on coherent performance was investigated. And then, a time synchronization method by using step frequency signal to replace linear frequency modulated signal was proposed. According to theoretical analysis, the effect of time synchronization error on coherent performance was reduced in our proposed method, which reduced the requirement of time synchronization accuracy into a realizable level. At last, the effectiveness of proposed method was verified by simulations.