The invention provides a method for preparing an acrolein catalyst by propylene oxidation. The method comprises the following steps: adding nitrate water solutions of Co and Ni into an ammonium molybdate solution under high-speed stirring, and adding a complexing agent and a surfactant to obtain sol; then adding nitrate water solutions of metal Fe and Bi to obtain water-based slurry, adding an organic solvent into the water-based slurry, performing uniform stirring, continuously supplementing the organic solvent, and separating water in the slurry to form an organic phase slurry system; drying and roasting organic slurry to prepare an inner-layer active ingredient and an outer-layer active ingredient; putting an inert alumina ball into a rotor drum granulator, slowly adding the mixed powder of the inner-layer active ingredient and crystalline cellulose, and adding a glycerin water solution for coating; after the inner-layer active ingredient is completely coated, slowly adding the mixed powder of the outer-layer active ingredient and the crystalline cellulose, and coating the outer-layer active ingredient; then performing drying and roasting to obtain the acrolein catalyst. The catalyst is stable in performance, and acrolein can be continuously and efficiently produced.