It is difficult to use the original seismic data directly to describe the thin reservoir of subtle hydrocarbon reservoir due to seismic resolution and wave form interference. The reflection coefficient inversion based on reflection coefficient data cube is an inversion technology：original seismic data are firstly processed by amplitude preserving and data denoising and time varying wavelet and space varying wavelet are extracted respectively to construct wavelet inverse transform factor，then frequency cube obtained by frequency division algorithm is selected to construct the geological conditions，and finally reflection coefficient data cube for data interpretation are calculated and obtained. In this way，all kinds of interference phenomena can be eliminated effectively and the resolution of seismic data can be improved. According to the problems of the thin sand body in the Cretaceous reservoir of Chepaizi area and the poor corresponding relationship between the reservoir and seismic reflection，the thin reservoir of subtle hydrocarbon reservoir in the study area was described based on reflection coefficient inversion. Results show that the sand bodies stretch along nearly south-north discontinuously in belt or in massive block，mainly distribute in the eastern and western coastal areas of the study area，which agrees with the sedimentary law that the Cretaceous mainly develops shore-shallow lacustrine sand body as well as regional fan delta sand body. According to the inversion results，the pinchout line of reservoir was extrapolated reasonably to the shore to expand the effective range of the lithologic trap distribution.