Abstract: The C-10 reservoir in Zhijing-Ansai area is analyzed with the data of core, rock thin section, casting thin section, mercury injection, SEM, X-ray diffraction and NMR. The results show that the lithology of C-10 reservoir is mainly arkose and lithic arkose, and the pore types are dominated by intergranular pores, feldspar dissolution pores and laumontite dissolution pores with good physical properties. The porosity and permeability are 11.4% and 2.35 mD respectively with strong heterogeneity. By studying the formation mechanism of physical differences between the east and west of the area, it is concluded that the reservoir physical property in the east is better than that in the west, mainly resulting from the good material foundation of the east and more acidic materials from C-9 source rocks, which promotes the development of dissolution pores. The Zhijing-Ansai area can be divided into 4 types of reservoir, among which the types Ⅰ and Ⅱ are mainly developed in the east, rare or undeveloped in the west. The type Ⅲ is widely distributed, but poor in physical properties, while the type Ⅳ is mostly non-effective reservoir.