Abstract: The present study relates to the intracrystalline diffusion in zeolite with secondary pores. Porous structure analyses and measurement of diffusivities of n-pentane are carried out on samples originated from the same type of NaY zeolite. The change of intracrystalline diffusivity of the zeolites with different secondary pores is investigated, and random walk simulation method is applied to the samples of same type. The results agree with the experimental data. Thus the intracrystalline diffusivities of zeolites with secondary pores can be estimated quantitatively.