The solubility of five groups of natural gas in reservoir formation water was measured under (333.2 to 393.2) K and (15.0 to 43.6) MPa. The formation water and corresponding natural gas were sampled in situ from a China oilfield. The range of total dissolved solids (TDS) of the reservoir formation water samples is from (8744 to 80634) mg.kg(-1). The mole fraction of methane in natural gas ranges from 0.7575 to 0.9449. The experimental results show that, with the increase of temperature and pressure, the solubility of natural gas in formation water goes through a minimum value under the experimental conditions. The solubility of natural gas in formation water was also influenced by a composition of gas phase and TDS of liquid phase. The salt effect becomes more significant in the high-pressure region.