The invention discloses a supported composite transition metal oxide, a preparation method thereof and an application thereof as a catalyst, and relates to the technical field of catalyst preparation.The preparation method comprises the following steps: fully and uniformly mixing an inert carrier with a pore channel structure, a transition metal salt and an oxidant to obtain mixed powder; addingan aqueous solution containing ammonia ions or an organic amine aqueous solution into a reaction kettle, wherein the aqueous solution containing the ammonia ions or the organic amine aqueous solutionis placed in the reaction kettle and is placed outside a reaction container; sealing the reaction kettle, and then placing the reaction kettle at a temperature of 120 DEG C to 200 DEG C for heating for 6-18h to make the transition metal salt and oxidant produce redox reaction to produce composite oxide, and loading the composite oxide in the channel of the carrier and the surface of the carrier toobtain the supported composite transition metal oxide. The preparation method of the catalyst is simple and can be operated easily, and the prepared catalyst has both activity and stability.