Equilibrium data on supercritical N-2 and CH4 adsorption on K02 activated carbon are presented in the temperature range 273-333 K and the pressure range 0-12 MPa. The adsorption potential theory was adopted to predict the adsorption equilibria of N-2 and CH4 in the whole range utilizing a single experimental isotherm. The methods in literatures for calculating the quasi-saturated vapor pressure and the adsorbate density of supercritical gases have been investigated in detail. It is demonstrated that the predicting accuracy is considerably more sensitive to the quasi-saturated vapor pressure than to the adsorbate density. Moreover, for different adsorbates, the appropriate approach to the important quasi-saturated vapor pressure is various in the same experimental range. A new viewpoint, based on the relationship between the research temperature ranges and the critical temperatures of adsorbates, was proposed to determine the exact method for the quasi-saturated vapor pressure in the application of the adsorption potential theory. (C) 2003 Elsevier Inc. All rights reserved.