Abstract: Dual mesoporous, micro-mesoporous and mesoporous molecular sieves were prepared and their pore structures were characterized by Ar adsorption and X-ray diffraction (XRD). The calculation methods of pore size distribution for the hierarchical porous molecular sieves were studied, to reveal the relationships among the adsorption-desorption isotherm, pore size distribution, pore shape and pore volume. The results showed that SF and BJH methods are reliable for microporous and mesoporous pores of the hierarchical porous molecular sieves, respectively, whereas NLDFT method is appropriate to calculate the full range pore size distribution. For the synthesis of mesoporous TS-1 zeolite, TPAOH promotes not only the generation of mesopores, but also the secondary crystallization.