Abstract: More and more reserves are discovered in low-permeability gas reservoirs and they urgently need to be developed. The reservoirs feature in low porosity, low permeability, and high water saturation. The NMR technique is used to probe into the irreducible water saturation of low-permeability gas reservoirs in Sulige Oilfield and the change of core irreducible water saturation under different gas flooding conditions. Research results show that the permeability has a high correlation with the irreducible water saturation. The lower the permeability is, the higher irreducible water saturation gets. The gas saturation gets lower too. So the irreducible water saturation can be used to indicate the potential of low-permeability gas reservoir development. The irreducible water saturation varies in different process of gas drive. The result provides scientific basis for the calculation of reserves in low-permeability water-cut gas reservoirs and the rational high-efficiency development of them.