The invention belongs to the technical field of chemistry and chemical engineering and in particular relates to a molybdenum-based composite metal oxide catalyst for synthesizing propenyl alcohol by glycerol and a preparation method of the molybdenum-based composite metal oxide catalyst. The chemical formula of the catalyst, namely molybdenum-based composite metal oxide, is MoxMyOz, wherein M refers to Fe, Ni or Zr. The preparation method of the molybdenum-based composite metal oxide catalyst comprises the following steps: dissolving and mixing soluble molybdenum salt and soluble salt containing tungsten, vanadium, iron, nickel and zirconium in an aqueous solution according to a certain ratio, and slowly dropwise adding carbonate or ammonium salt as a precipitator until the solution is fully precipitated; and ageing precipitate in the aqueous solution, then washing the precipitate by deionized water until the pH value of filtrate is neutral, subsequently drying a filter cake in a drying oven, then increasing to a certain temperature by temperature programming, and roasting to obtain the catalyst. The preparation method of the catalyst is simple in process; according to the prepared catalyst, a glycerol conversion rate is maintained to be greater than 90% while propenyl alcohol selectivity reaches over 40%.