Abstract: The sorption of C5 paraffins in AlPO4-5 molecular sieves at 303K～675K was simulated by Monte Carlo method with Cerius-2 developed by MSI. The Henry constant, the isotherms and the average potential energy of C5 in the framework were obtained. It was observed that the sorption capacity of 2-methylbutane was higher than that of cyclopentane at 373 K, and this sequence was reversed at 473 K; the sorption loading of cyclopentane was higher than that of 2-methylbutane and n-pentane at 573 K under 0～20 kPa, which could be well interpreted based on the packing fashion of sorbates in the channel of AlPO4-5 molecular sieves. Moreover, the average potential energy of C5 decreased with the increase of the loadings at higher loadings. A sharp decrease of average potential energy was found for both of 2-methylbutane and cyclopentane when the loading was higher than 1 molecule/unit cell.