Thickness of reservoir has a direct and close contact with oil and gas exploration and development, reservoir thickness is directly related to success and failure of the exploration and development. The main problem of the Seismic exploration is the limit of the resolution, geophysical workers have done a lot work, but the effect has been not obvious. Mainly to the following questions: 1、it is difficult to determine the boundaries of the reservoir；2、the limits of the resolution still exists. In this paper, through the study of the high-resolution sequence Stratigraphy and fine calibration, we used the sequence boundary and flooding surface to build the initial model, and then the density inversion was done to indentify the oil and gas reservoir. On the basis of the inversion, the density ranges of the sandstone in the sequence were calculated through geostatistics, and then we correctly calculated the thickness of the sandstone in every sequence, in this way we not only solved the problem of reservoir boundaries, but also improved the resolution.