Abstract: The four component ocean bottom seismometer (OBS) is a new instrument. The seismic data obtained from the OBS contains a large amount of information; it has high SNR (signal-to-noise ratio) and abundant frequency compared to streamer data. The study of deep crustal structure has achieved good progress using OBS data, but the studies of oil-gas exploration and basin structure have achieved less progress. Using large capacity air-gun array (0.083 m³) as source in the northwestern South China Sea, we obtained seismic information from reflection and refraction data from the OBS, and then interpreted it for oil-gas exploration in an attempt. To properly use the OBS seismic data, we must adopt the method that is different from conventional seismic data processing method, in this paper we proposed a new method which used the method of mirror time migration of pre-stack processing. The method includes the OBS data vector fidelity processing, the P (pressure) and Z (vertical) component of the pre-stack processing and image of pre-stack time migration processing; the vector fidelity processing is to control and correct the positioning in space (x, y, z) and in time (clock drift), and the geophone sensor orientation (vertical and horizontal components); the P and Z component of the pre-stack processing includes zero phase processing and seismic- channel correcting, P and Z summation, residual static correction, image superposition and multiple attenuation; mirroring the pre-stack time migration processing is to use the multiple wave imaging technology. Using the mirror of pre-stack time migration processing, good imaging profile can be obtained.