Intracrystalline diffusivities for aromatic carbon in ZSM 5 were measured by ZLC method. Experiments were analyzed by two traditional methods (LT method and ST method) and a new full range method. The traditional mathematical description of the ZLC technique by LT method or ST method will cause deviation unavoidably. The new full range method avoids the problems caused by the traditional methods, so it is more suitable to analying ZLC experiments. Diffusion coefficients calculated by FR method are greater than those by LT method, but smaller than by ST method. Experiments were analyzed by two traditional methods (LT method and ST method) and a new full range method. The traditional mathematical description of the ZLC technique by LT method or ST method will The new full range method avoids the problems caused by the traditional methods, so it is more suitable to analying ZLC experiments. Diffusion coefficients calculated by FR method are greater than those by LT method, but smaller than by ST method.