Abstract: The kinetics of coke formation on SAPO-34 catalyst in the transformation of methanol to olefins was studied in a fixed bed reactor and the relations in a type of Voorhies equation between coke deposition and reaction temperature or the ratio of catalyst-to-methanol were obtained, which could be used easily in practice. In the condition of 450 ℃, 15 h－1 methanol WHSV and 25 min TOS, an obvious coke distribution was found in the catalyst bed with a coke content of 9.56% at the inlet of catalyst bed and 3.20% at the outlet, which corresponded to a deactivation mainly in parallel with the main reaction. The coke was formed mainly in parallel with the formation of hydrocarbons, and all the products came from intermediates generated from methanol. On the basis of this mechanism, a kinetic model for coke formation which related the coke deposition with the methanol converted in reaction was induced. This kinetic model showed a good agreement with the experimental observation and also could be used easily.