With some engineering geology features of low-porosity and permeability，high capillary pressure，developed natural cracks and ultra-low water saturation，the tight sandstone gas reservoirs have strong imbibition phenomenon，which could lead to water phase trapping damage due to countercurrent capillary imbibition of water in reservoir even under conditions of negative pressure difference. Some typical tight sandstone core samples from Ordos basin with different permeabilities of less than 0.2×10-3 μm2，between 0.2×10-3 and 0.5×10-3 μm2 and higher than 0.5×10-3 μm2 were selected to evaluate the counter current capillary imbibition and water flow-back during gas driving. The process of water phase trapping damage was simulated under negative pressure difference and the effect of countercurrent water imbibition on the gas permeability was discussed to know the damage degree. The results indicate that the decrease of gas permeability caused by the countercurrent imbibition under the negative pressure difference is more likely to have some characteristics of step change controlled by the physical properties of cores. The permeability damage ranges from 26.5% to 34.9% with the average of 29.8% under the same negative pressure difference. The lower the negative pressure difference is，the stronger the countercurrent imbibition is，which leads to deep entrance of water and more serious water phase trapping damage. So，safe operation，water flow-back in reservoir and other factors should be considered when the drawdown pressure is fixed during underbalanced drilling and completion and development.