Coke formation in the conversion of methanol over faujasite, mordenite, and ZSM-5 zeolite catalysts was studied. Coke formation was dependent on the pore structure of zeolites catalysts. For faujasite structures, coke was deposited at the internal surface of 3-dimensional pore, reducing the effective pore size reduction retarded the coke formation by diffusion limitation. The sharp decrease in the surface area and the slow rate of coke formation in mordenite were due to the blocking of pores by the coke deposited. The structural stability for water due to its hydrophobicity and intersecting channel pore structures seemed to be responsible for the slow rate of coke formation in the conversion of methanol to hydrocarbons over ZSM-5 zeolite.