The invention relates to an offshore streamer broadband wide-azimuth seismic exploration method. The offshore streamer broadband wide-azimuth seismic exploration method comprises the following steps of: establishing a three-dimensional seismic geologic model suitable for a stratigraphic structure of a target area, based on geological horizon, rock velocity and density data of the target area for previous offshore seismic exploration; optimizing the type of a wide-azimuth observation system and the aspect ratio of streamers, so as to obtain a wide-azimuth observation system type and a streamer aspect ratio that are suitable for the target area; optimizing three-dimensional curved streamer parameters, so as to obtain optimized three-dimensional curved streamer shape and streamer parameters; optimizing multi-point depth-variable random delay excitation parameters, so as to obtain excitation delay time series distribution corresponding to each synchronous source during excitation at different excitation points; in the target area, carrying out actual offshore streamer broadband wide-azimuth seismic acquisition by the three-dimensional curved streamers during multi-point depth-variable random delay excitation, so as to obtain actual acquisition mixed source shot gather records for the series of multi-point depth-variable random delay excitation.