Abstract: Study has been conducted on reservoir physical property,diagenetic characteristics and the main controlling factors on the development of deep tight gas reservoir in Xihu Sag with the data of thin-sections of core,physical property data,scanning electron microscopy,X-ray diffraction and other analytical data.The study results show that the deep reservoirs of Xihu Sag are low porosity and low permeability reservoirs.Reservoir "dessert" with secondary pores is common.Compaction and cementation are the main factors leading to deep tight reservoir.Dissolution and overpressure are the main controlling factors for the development of these deep reservoir "dessert".