Abstract: Based on the basic data of physical properties and thin sections, the sedimentary, petrological characteristics, physical properties, pore types and distribution characteristics of the deep reservoirs in Xihu Sag are analyzed. It shows that the deeps and stone reservoirs have multiplicity rock composition and medium component maturity. The content of soluble components such as feldspar and cuttingsis favorable are high. It is easy to be dissolved to form a large number of secondary pores, and has positive effect on the physical properties.The environment of Pinghu Formation in Baochu Slope includes the distributary channel and sand dam of delta.The typical of "mud-encased sand" mode is beneficial to form the secondary pore growth zones with multiple stages. Huagang Formation has a different environment with braided channel and braided distributary channel in the central anticline belt. The sand bodies are extensively distributed. The typical of "cycle" mode is beneficial to the dissolution of thick sand bodies in the direction where the sandstone in the central anticline beltis connected with the mudstone in Santan Depression. And it has favorable conditions for the formation of large oil and gas reservoirs.