The influence of mobile and bound water on seepage capability of a low-permeability sandstone gas reservoir was studied and formulas were derived to calculate gas well production rate using cores from Xujiahe low-permeability sandstone gas reservoir in China. It is shown that mobile water in the well exerts a stronger negative effect on gas production than bound water. If the pressure gradient is too steep, a small part of the bound water may turn into mobile water, whereupon the gas seepage efficiency falls. So, use of controlled pressure is recommended for gas production, which in the end enhances the gas recovery efficiency of the reservoir.