Abstract: In this paper, we calculated the depth of the upper and lower boundaries of the Mesozoic for the southern part of the East China Sea Shelf Basin based on the newly acquired seismic, gravity and the drilling data.As the result, the residual thickness of the Mesogoic is obtained. The method of multi-interface density inversion is adopted for the calculation of residual thickness. On the basis, we analyzed and studied the distribution pattern of the Mesozoic. The research shows that, except the peak of the Yandang low uplift, where the Mesozoic is partly missing, the Mesozoic strata are widely distributed in the Southern East China Sea Shelf Basin. The data also shows that the residual thickness of the Mesozoic are unevenly distributed in different tectonic units.In a general view, it is thicker in the east and thinner in the west and also shows a structural pattern of "north-south block". The Keelung Sag remains the sedimentation center of the study area.