Sb/ZSM-5 was obtained by solid-state reaction with the mixture of Sb 2 O 3 and zeolite HZSM-5 under a dry nitrogen flow at 773K. Characterization of the treated zeolite was undertaken with XRD, 27 Al MAS NMR, BET, TGA and FT-IR. The results revealed that part of the antimony oxides migrated into the channels of zeolite, and decreased the Brönsted acid sites in Sb/ZSM-5 remarkably. The other part of antimony oxides together with the amorphous alumino-silicate in the products distributed on the external surface of zeolite ZSM-5 and modified it, while the framework of ZSM-5 in crystal phase was retained. The structure of occluded antimony oxide inside the channels of ZSM-5 was studied by XRD Rietveld method. The result showed that their structure can be described as a chain of non-perfect [Sb 5 O 5 (H 2 O) 2 ] n 5 n + , which is parallel to the straight channel of ZSM-5. There is about 0.6 [Sb 5 O 5 (H 2 O) 2 ] 5+ unit in every cell of the ZSM-5 on an average.