Abstract: The adsorption of two representative N-nitrosamines with larger molecular volume than the pore size of zeolites, N-nitrosohexamethyleneimine (NHMI) and N’-nitrosonornicotine (NNN) on zeolite KA and NaA were investigated in this article, in order to explore how the small pore zeolites adsorb and separate those guest molecules with bigger volume. Both NHMI and NNN could be adsorbed on NaA or KA zeolites and degraded in the process of temperature programmed surface reaction (TPSR), though the pore size of adsorbent was much smaller than the molecular size of the adsorbate. Several possible adsorption models of NHMI and NNN were assumed and discussed on the basis of simulation for the structure of N-nitrosamines, but only the insertion of －N－N=O group in the channel of zeolites was found to be the feasible one in accordance with the experiments of adsorption and TPSR. Through such insertion-adsorption, many pollutant species with big molecular size in the environment can thus be adsorbed and separated by use of zeolite molecular sieve materials.