A catalytic conversion method for preparing propylene and aromatic hydrocarbons comprises the following steps: hydrocarbon raw materials with different cracking performances are contacted with a catalytic cracking catalyst to carry out cracking reaction in a fluidized-bed reactor under the conditions that the temperature is 450-750 DEG C, the weight hourly space velocity is 0.1-800h<-1>, the reaction pressure is 0.10-1.0MPa, the weight ratio of the catalytic cracking catalyst to the raw materials is 1-150 and the weight ratio of water vapor to the raw materials is 0.05-1.0, the spent catalyst and reaction oil and gas are separated, the spent catalyst returns to the reactor after the regeneration, the separated reaction oil and gas are separated to obtain target products of low-carbon olefins, aromatic hydrocarbons and the raw materials for re-cracking, wherein the raw materials for re-cracking are re-cracked after hydrotreating. The method can product the propylene and other low-carbon olefins from the heavy raw materials to the maximum extent, wherein the yield of the propylene is more than 40 percent by weight; meanwhile, the method can co-produce toluene, xylene and other aromatic hydrocarbons, and the yield of the dry gas is unexpectedly reduced by more than 80 percent by weight.