Abstract: To identify the controlling factors on complex gas-water distributions in tight sandstone gas reservoirs, taking Xu-6 gas reservoir of Guang’an gas field in Sichuan basin as an example, and based on the data of logging, connecting-well section, seismic section and mercury injection, the paper studies the controls of source rock distribution, reservoir physical properties and structural amplitude on gas-water distributions in gas reservoirs comprehensively. The results show that the source rocks interbedded with thin sandstones supply hydrocarbons sporadically, which is the root cause of multi-gas intervals and complex gas-water distributions in Xujiahe formation; with the same hydrocarbon supply conditions, natural gas will first migrate to and accumulate in good quality reservoirs, which results in varied differentiation of gas and water in different blocks; structural amplitude has impacts on gas and water differentiation degrees in tight sandstone gas reservoirs, and the higher the structural amplitude is, the more sufficient the gas and water differentiation will be. Therefore, the gas-water distributions in tight sandstone gas reservoirs are mainly controlled by hydrocarbon source rock distribution, reservoir physical properties and structural amplitude and so on