Four different samples of pure scheelite α-Bi2Mo3O12 were synthesized by the fast microwave-assisted hydrothermal method. By adjusting the pH in the preparation process, the morphologies and structures of the synthesized catalysts were changed. TG, XRD, SEM, TEM, BET, and XPS analyses were used to investigate the characteristics of the catalyst. The sample of α-Bi2Mo3O12 was prepared at a calcination temperature of 500 °C and pH = 1 had the highest specific surface area propylene selective oxidation properties. The conversion of propylene was 28.3% and the selectivity of acrolein was 86.4%. Compared with α-Bi2Mo3O12 prepared by co-precipitation and normal hydrothermal method, α-Bi2Mo3O12 prepared by microwave hydrothermal method has higher propylene oxidizing activity. The conversion of propylene is negatively correlated with the crystallinity of the catalyst. This is due to the fact that higher crystallinity inhibits the lattice oxygen flow between the lattices, thus inhibiting the selective oxidation and reducing the conversion of the reaction. The oxygen mobility of α-Bi2Mo3O12 samples was characterized by XPS. The results showed that the conversion of propylene of α-Bi2Mo3O12 were positively correlated with its oxygen mobility strength. A probable mechanism for the selective oxidation of propylene was proposed. This work not only offers a high-efficiency method for the rapid preparation of bismuth molybdate catalysts but also extends the application of microwave-assisted hydrothermal synthesis in the field of selective oxidation of propylene. [ABSTRACT FROM AUTHOR]