Porous particles used in combustion or catalysis were made by random walk method. The fractal characteristics of the porous particles are close to that of real ones. Based on the particle model

gas diffusion was investigated in the porous particles. Diffusion control equations were established according to the kinetic theory of gases and statistical thermodynamics. The effect of pore characteristics on gas diffusion was analyzed. The relationships between the specific area

average pore diameter and porosity with the diffusion coefficient were obtained. The results indicate that the gas diffusion coefficient decreases with the increase of specific area of pores. Gas diffusion coefficient increases as a power function of average pore diameter

and the exponent that represents the sensibility decreases linearly with the increase of porosity.