A deep seismic sounding experiment was carried out for the first time in the Bohai Sea using large volume air-gun array and Ocean Bottom Seismometers (OBSs). Fifty-one OBSs were deployed along a NWW-SEE line perpendicular to the strikes of the regional tectonics and fifty were recovered successfully. Experiment outcome showed the air-gun array used during the experiment had enough power; primary data analysis indicated the OBSs recorded rich seismic phases including Ps, Pg, PmP and Pn. Initial first arrival tomography results show that the shallow layer with depth of less than 9 km has obvious heterogeneity in the lateral direction, the depth of the Cenozoic sedimentary basement is 5~6 km in the Bozhong area and the corresponding crystalline basement depth is about 9 km, and an U-shaped lower velocity body which has the trend to cut through the lower layer can be found in the Tanlu fault zone. This experiment is a successful case of the deep structure exploration in the Bohai Sea. It not only fills in the blanks of deep seismic sounding database, but also supplies fundamental information for the research of deep crustal structure around Bohai area and the development of Bohai Bay Basin.