The hydrocarbon deposition on the catalyst is known to be crucial to the methanol-to-olefin conversion reaction.In this paper,the effect of catalyst organic deposition level on the product selectivity for a SAPO-34 catalyst is reported.The test results obtained from a fixed fluidized bed reactor system indicated that ethylene selectivity increased faster than that of propylene with increasing organic deposition up to about 6 wt% whereas the selectivity to butenes decreased.