Abstract: The study on KX structure in the Xihu depression is one of the key regions of the present offshore exploitation targets. The petrographical reservoir characteristics, the reservoir development characteristics and the main control factors on hydrocarbon accu-mulation have been studied by using large number of thin-sections and core data, and other analytical testing data. The study results indicate that the reservoir rocks are dominated by feldspar lithic quartzite sandstone, with rich pore-filling contents, being well-sorted, with low composition maturity, and high-rounded. The pore types are mainly secondary pores. The throat types are mainly laminated and curved lamellar throat. The pore structure feature is mainly mesoporous-small throats and small pores throats. The reservoirs are characterized by low porosity and permeability. The reservoir rocks were deposited under the control of distributary channel, and the main controlling factors on sandstone reservoirs in Pinghu formation are diagenetic compaction, cementation and dissolution.