Abstract: The M well area of RY depression is located in the slope belt of the shallow water delta front, where underwater distributary channel sandstone is mostly developed. The thickness of sandstone reservoir is thin and changes quickly the horizontal direction. In addition, the sand body in the same period is featured by multiple oil-water systems. Hence, it is easy to form lithologic reservoirs, which is very difficult to predict by conventional inversion methods. In this paper, we introduce seismic phase interface, such as structural fluctuation, lithologic change and sedimentary environment change, to reduce the multi-solution of inversion. Meanwhile, we combine chaos theory with inversion algorithm to modify adaptively regularization operator. Doing like that can adjust stability and resolution of inversion to reach the optimal balance, which not only avoids the occurrence of chaos, but also reveals the information of thin layer to the maximum extent from seismic data. The practical application of well M shows that phased chaos inversion can highlight the detailed changes of seismic waveform, accurately describe the positions of reservoir annihilation and bifurcation points, and achieve the purpose of accurately predicting lithologic oil and gas reservoirs. This paper is of great guiding significance for subsequent exploration and development of lithologic reservoirs.