Field observation, logging data, core thin section study and physical property detection indicate that sandstone of the Member 4 of the Upper Triassic Xujiahe Formation in the Fenggu structure is a pore-fissure reservoir which is characterized by low porosity, low permeability and strong heterogeneity with local high porosity and permeability. The reservoir property is controlled by sedimentary and diagenesis type. The most favorable lithologic character is gray, grayish, medium-and coarse-grained lithic sandstone and lithic quartz sandstone in stream channel facies, intertidal and subtidal channel, sandbar and swash bar. The sandbody is characterized by large thickness and rapid changing lithologic character with carbonate cement. Secondary corrosion played an important role in improvement of reservoir property.