The invention relates to a method for directly preparing propylene from crude methanol, wherein, in an integrated unit for preparing the methanol and preparing the propylene from the methanol, the crude methanol directly enters a multistage adiabatic fixed bed reactor loaded with an acid molecular sieve catalyst without rectification and purification to prepare low carbon olefin with the propylene as a main component. In the method, steam and circulating hydrocarbon as diluent, and a mixture of the crude methanol and water is used for interstage cold shock to control reaction temperature of the reactor in each stage. The method helps obtain high propylene yield, and obviously reduce investment and energy consumption of the integrated unit for preparing the methanol and preparing the propylene from the methanol.