A commercial zeolite pellet is formed by binding large numbers of small crystals with microporous material. Its Micro-structure has great affects on the gas adsorption process. In this paper, the physical and mathematic models of the adsorption process for a single pellet are established. The N2 adsorption properties in a 5A zeolite pellet are studied. Very detailed results of intra-pellet adsorption process are obtained. The impacts of crystal size, pellet porosity, diffusion coefficient of the binding materials and crystals on the adsorption rate are studied.