The Bohai Bay basin is a principal contributor to oil and gas production not only in offshore China but also on a global scale, with its hydrocarbon resource distribution exhibiting marked differences between marine and terrestrial areas, a pattern intimately linked to the basin' s crustal structure. In order to clarify the crustal structure of the Bohai Bay basin, this study leveraged terrain and gravity data to reveal the distribution of basin faults and the fluctuations of the Moho interface. NVDR- THDR technology and Euler deconvolution were utilized to ascertain the planar locations of the faults and their apparent depth distributions. Minimum curvature technique for potential field data separation and the fast solution of forward and inverse problems for gravity fields in a dual interface model were applied to obtain the fluctuations in the Moho interface. The investigation uncovered significant contrasts between marine and terrestrial areas regarding both fault distribution and Moho characteristics: marine areas feature faults trending in both NNE—NE and WNW—NW directions, whereas terrestrial regions predominantly exhibit NNE—NE trending faults. Compared to terrestrial settings, marine faults tend to be shallower and show more intense late- stage activity. Sags in marine areas display shallower average Moho depths, thinner crustal thicknesses, and higher mean values for the sum of Moho stretching factors and crustal stretching factors relative to terrestrial sags. These findings indicate that marine areas have experienced greater tectonic deformation, creating favorable conditions for the formation of hydrocarbon- prone zones and hydrocarbon migration and accumulation. Conversely, terrestrial environments present less advantageous conditions, directly impacting the differential distribution of hydrocarbon enrichment within the basin. Consequently, the spatial distribution hydrocarbon resources in the Bohai Bay basin is tightly connected to the distribution of faults and fluctuations of the Moho interface. This research furnishes a scientific foundation for guiding further oil and gas exploration efforts in the basin.