Abstract: ABSRTACT: At present, the N gas field in Xihu Sag, East China Sea, has basically achieved the full coverage of 3D seismic data of towing cable. However, because of the narrow azimuth, the underground wave field information could not be obtained in all directions, which leads to the deviation of the imaging of complex faults, which can not meet the requirements of fine exploration and development of oil and gas fields. The wide azimuth seismic data can obviously improve the imaging of steep dip angle and complex structure compared with the conventional narrow azimuth seismic data, but the cost is high and the construction is difficult. Therefore, the wide-frequency and high-density 3D seismic data acquisition was deployed in the west slope of Xihu Sag, which is perpendicular to the original narrow azimuth 3D seismic acquisition direction, and the quality of seismic data and the imaging effect were significantly improved. Progresses and findings were obtained in the following aspects. First, the vertical and horizontal resolutions of seismic data were improved and the profiles were more natural by applying the 3D ghost wave suppression technology onboard main and auxiliary ships. Secondly, the potential of existing seismic data was fully exploited by applying the matching processing technology of new and old data, and the seismic data obtained after the matching processing showed a better calibration effect, higher correlation coefficient, better seismic continuity, and better energy focus. Thirdly, the precise velocity modeling technology based on multi-information iteration can be used to obtain a more accurate velocity model, which effectively improved the depth prediction accuracy. Fourthly, the frequency band of seismic data can be widened using the frequency extension technology of curved wave domain, such as curved wave domain transform decomposition, high-frequency information difference etc. Well drilling showed that the application of seismic data fusion technology could improve the imaging accuracy of seismic data with more-accurate depth prediction. At the same time, the resolution of seismic data and the effect of reservoir prediction were obviously improved. This study provided a strong support for the deployment of subsequent development wells.