A kinetic model for the methanol to olefins (MTO) process on a catalyst based on a silicoaluminophosphate SAPO-34 has been proposed. The model takes into account four individual steps for the production of ethene, propene, butenes, and remaining hydrocarbons (pentenes + paraffins). The kinetic parameters have been obtained by experimentation in an isothermal fixed-bed reactor, in the 623-748 K range. In virtue of the results, it has been proven that the water introduced in the feed (required for attenuation of coke deactivation) inhibits olefin formation. This inhibition is taken into account in the kinetic model.