Abstract: The calcarenaceous sandstone reservoir in the fourth member of the Xujiahe Formation in Fenggu area of the Western Sichuan Depression is a typical tight sandstone reservoir characterized by high content of carbonate debris(accounting for over 90% in total debris),well-developed carbonate cementation,low porosity and low permeability;however,under the background of general dense,favorable reservoirs also develop in some intervals with the porosity of over 12%.The analysis of reservoir feature and diagenesis has indicated that the differential cementation of reservoir calcite is the key for the preservation of primary pore in high-quality reservoir.Then disruption communicates reservoir and acid fluid of hydrocarbon emplacement,improving reservoir quality.The later hydrocarbon charge protects reservoir porosity.