Abstract: morphology and specific surface area (SSA)for n1e products after acid treatment of palygorskite were investigated by TEM and BET-SSA and the reaction mechanism between palygorskite and acid was discussed. The results indicate that the reaction between palygorskite and acid be longs to a reaction of proton diffusion from exterior surface rather than from channels. The rate of reaction is controlled by diffusion through the file of silicon acid which is formed by the reaction. The reaction yields concurrent dissolution of tetrahedron and octahedron cations from two ends of the palygorskite crystals and variant dissolution of the tetrahedron and octahedron cations from the columns. The mesoporous structure of palygorskite after acid treatment is caused by the partial dissolution of tetrahedral silicon from the columns. SSA increase of palygorskite is resulted from asymmetrical and discontinuous dissolution of octahedral cations and local dissolution of tetrahedral silicon, which results in opening of channels and enlargement of aperture diameter.