Abstract: With the progress of oil and gas exploration in deep water areas of the western South China Sea, single pieces of 3-D seismic data, which have inconsistent quality caused by different acquisition factors and processing techniques, is no longer able to meet the requirements of overall exploration and resource evaluation. To solve the problem, we applied the matching and concatenating processing technique combined with multiple suppression technique to unify data quality and improve the signal to noise ratio for the middle to deep layer. Initial velocity modeling, which is constrained by strata velocity in deep water area, was then established on this basis. Grid tomography of high precision was applied to improve imaging accuracy. The results showed that the problem of inconsistent data quality in deep water area was solved and the imaging of the middle to deep layer was much improved.