The deep-water submarine fans of the Miocene Meishan Formation in Ledong-Lingshui sags in the west area of Qiongdongnan Basin,are the main gas exploration area.A comprehensive analysis is conducted to study the diagenesis and its influence on the porosity evolution of deep-water submarine fan reservoir under the background of high temperature and overpressure,by means of thin section,X diffraction,scanning electron microscopy(SEM),cathodoluminescence,stable isotope,and fluid inclusion analysis.The results show that:(1)The rock types of deep-water submarine fan reservoir in Meishan Formation are mainly lithic quartz sandstone and feldspar lithic sandstone.The reservoir properties are mainly characterized by low-medium porosity and low to ultra-low permeability,with strong heterogeneity.(2)The reservoirs evolved as follows:early compaction and clay mineral cementation→the first phase of low mature oil filling→feldspar dissolution,secondary enlargement of quartz,ferrocalcite cementation→the second phase of higher mature oil-gas filling→(ferrodolomite)dolomite cementation,quartz and its secondary enlargement dissolution,overpressure formation→the third phase of high mature natural gas accumulation→late CO2 charging,hydrothermal action.(3)The reservoir pore evolution is controlled by the compaction-cementation with overpressure protection and dissolution.Early compaction and cementation are the main destructive factors.The pore preservation of overpressure and dissolution are the main constructive factors.The influence degree of diagenesis on the deep-water submarine fan reservoir is different in the different tectonic zones,resulting in the current differential pore characteristics.