Abstract: It is difficult to acquire accurate seismic velocity from the marine strata in the South Yellow Sea Basin due to its special seismic geological conditions. From multi-channel seismic data, we extracted reliable Mesozoic-Paleozoic velocity of marine strata by combining the velocity analysis together with multi-data controlling, first-break tomographic inversion and layer-constrained grid tomographic technique. The velocity distribution pattern of marine strata in the South Yellow Sea is then summarized according to extracted seismic velocity and drilling information from the Lower Yangtze region. The distribution of strata velocity in this area shows a pattern of alternation of high and low velocity with mutation and inversion. The marine lower tectonic layer is high in velocity and the velocity difference between layers is small. The velocity distribution of marine lower tectonic layer is still uncertain because of lacking in drilling data in the sea area.