Computer NPT ensemble simulation of the chemical potentials and Henry constants for methane and benzene in infinite dilute aqueous solutions was carried out in terms of the thermodynamic integration with a coupling parameter

and the preferential sampling method. The TIP4P and OPLS potentials were used for the description of the molecular interactions of water and organic substances

respectively. The Ewald method was incorporated into the long range correction for the interaction between water molecules. The simulated results were in fair agreement with experimental data within the errors for MC computer simulation

which indicated that this method could be applied to the predication of the properties for organic substances in infinite dilute aqueous solutions.