Tight sandstone gas reservoirs are prone to aqueous phase trapping damage（APTD），due to narrow pore throat，high capillary pressure，locally ultra-low water saturation，which will reduce the productivity of the gas wells. The extent of the APTD was evaluated with the methods of phase trapping factors in the upper Shihezi formation in M gas field of Ordos basin. Imbibitions tests and liquid retention evaluations were conducted to analyze what cause the APTD，and the prevention and removal of the APTD was explored through using FW-134，a surface-modifying agents for wettability modification. Results showed that there was potentially strong damage of water phase trapping in the upper Shihezi formation. The better the physical properties of the reservoir was，such as He2+3，the easier the water imbibitions and flow back. The average liquid flowback rate in the upper Shihezi formation was 10%—47%，and the average flowback rate of filtrate was 22.4%—32.3%. The use of quaternary ammonium fluoride to change the surface to gas wetting effectively inhibited the liquid imbibition in tight stone. The flow back rate of liquid increased from 56.3% to 83.4%. Gas permeability recovery of the cores was increased from 66.1% to 88.2% after treated by FW-134. Wettability alteration from water wetting to gas wetting is an important way to prevent and alleviate the APTD in tight sandstone gas reservoirs，which is significant to recovery of the gas well productivity.