Permeation mechanism of inorganic gases was studied experimentally, and theoretically through microporous silica membranes prepared by the sol-gel method. Inorganic gas permeation was measured using the membranes with subnano pores in diameter. The permeance of He increased with increasing temperature for various cases, while that of CO2, O-2 and N-2 decreased. In particular; the observed temperature dependency, of CO2 was greater than those of other gases. In such small pores, the interaction energy between a permeant molecule and the pore wall call affect gas-permeation properties. A simple gas-permeation model is used considering the effect of the attractive or repulsive pore-wall potential field, which deviates from thc ambient gas phase of the gas molecule concentration (pressure) in a pore. Thc model call explain the experimental gas-permeation properties successfully Potential curves of CO2 and N-2 in a silica pore were also calculated to predict the permeation ratio of CO2/N-2. This model call help understand further the gas-permeation mechanism in micropores.