A new model for calculating high-pressure solubility of gas in aqueous electrolyte solution is proposed based on non-primitive mean spherical approximation (MSA) equation and perturbation theory. The non-primitive MSA is used to describe the interactions of ion-ion, ion-dipole and dipole-dipole. The Lennard-Jones potential energy as a perturbation term is introduced to represent the dispersion effects among particles including both ion and molecule species. The water molecule parameters are derived from the experimental saturated vapor pressure data of pure water and the ion parameters of cations and anions are obtained by fitting experimental mean ionic activity coefficients. The parameters of gas solved in aqueous salt solution are only derived from the experimental solubility data of gas in pure water. The equation of state derived from the previous procedures have been used successively to predict gas solubility in aqueous salt solution using the pure-component parameters,