The conversion of methanol to olefins (MTO) over the SAPO-34 catalyst in fixed-bed microreactor was studied. The effect of reaction temperatures for methanol conversion to olefins and byproducts was investigated. A temperature of 425 ℃ appeared to be the optimum one suitable for conversion of methanol to olefins. Since the presence of water could increase the olefins selectivity, the methanol conversion reactions with mixed water/methanol feed were also studied. The effect of weight hourly space velocity on conversion of methanol was also studied. The results indicated that the olefins selectivity was significantly increased as WHSV increased till approximately 7.69 h-1 then it began to level off. Different factors affecting the catalyst deactivation rate was studied, showing that the catalyst deactivation time was dependent on reaction conditions, and temperatures higher and lower than the optimal one made the catalyst deactivation faster. Adding water to methanol could slow down the catalyst deactivation rate. The conversion of methanol to olefins (MTO) over the SAPO-34 catalyst in fixed-bed microreactor was studied. The effect of reaction temperatures for methanol conversion to olefins and by products was investigated. A temperature of 425 ° C to be the optimum one suitable for the conversion of methanol to olefins. the result of water could increase the olefins selectivity, the methanol conversion reactions with mixed water / methanol feed were also studied. The effect of weight hourly space velocity on conversion of methanol was also studied. that the olefins selectivity was greatly increased as WHSV increased till about 7.69 h-1 then it began to level off. different factors affecting the catalyst deactivation rate was studied, showing that the catalyst deactivation time was dependent on reaction conditions, and temperatures higher and lower than the optimal one made the catalyst deactivation faster. Adding water to methanol could slow down th e catalyst deactivation rate.