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Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere (designated as NaY/kaolin composites ) separately, using a high precision intelligent gravimetric analyzer (IGA). The adsorption iso-therms showed normal Langmuir type-?behaviors. The increased adsorption heat with an increasing p-xylene coverage sup-ported a mechanism of phase transition, diffusion and re-arrangement of p-xylene molecules during the adsorption process. The rearrangement seemed to be most pronounced at an adsorption loading of 2.13 and 2.29 mmol/g for NaY zeolite and NaY/kaolin composites respectively. Compared with NaY zeolite, a 2—3 times higher in the diffusion coefficient of p-xylene was observed on NaY/kaolin composites when the pressure was more than 50 Pa. Temperature-programmed de-sorption (TPD) of p-xylene on two samples from room temperature to 450℃ at a special loading has also been investigated by IGA. Results showed only single desorption peak appeared for NaY zeolite, indicating that adsorption can only occur in the super-cage structure. Comparably, there were two different peaks for in-situ synthesized NaY zeolite, corresponding to the two thermo desorption processes in both super-cage structure and the channels provided by kaolin, respectively.