Abstract: As the hotspot and emphasis of petroleum exploration in east China, sand lens reservoir plays an important role in the increase of petroleum reserve. Therefore, it is significant to do research on sand lens reservoir—its hydrocarbon accumulation mechanism, its quantitative evaluation and the forecast of its oil-bearing properties. Based on systematic analysis of hydrocarbon accumulation drive and resistance, we applied numerical simulation and geological statistics to construct geological model as well as mathematic model of hydrocarbon dynamics for sand lens reservoir, and to simulate hydrocarbon accumulation process. The research results show that major accumulation drive consists of capillary pressure difference between sandstone and mudstone, diffusion power resulted from hydrocarbon generation in mudstone and expansion power caused by hydrocarbon generation in mudstone. And the major accumulation resistance includes capillary pressure, sticky and absorption resistance in sandstone. The formation of lithologic reservoir in the Dongying depression was controlled by many factors including hydrocarbon expulsion intensity of mudstone, porosity and permeability of sandstone, buried depth, the ration of thickness of sandstone and thickness of mudstone. The formation of sand lens reservoir can be divided into several stages, and only at the late diagenesis stage, the accumulation drive was greater than the resistance and as a result hydrocarbon filled in sand lens, which shows there exists a threshold buried depth for sand lens. Based on hydrocarbon accumulation dynamics, the authors also constructed quantitative relation between accumulation dynamics and oil-bearing properties, which affords a good means to forecast saturation and its saturation distribution in plane of sand lens pool.