The invention discloses a preparation method of a mixed metal oxide thin film catalyst for a hydrocarbon oxidation reaction, and belongs to the catalyst preparation technical field. The preparation method comprises the steps: firstly, preparing a layered double hydroxides (LDHs) thin film precursor MMnAl-LDHs on an anodic alumina substrate by an in-situ growth technology, carrying out thermal decomposition to obtain a mixed metal oxide (MMO) thin film MMnAl-MMO, taking a reaction of catalyzing aromatic hydrocarbon to be oxidized to synthesize aldehyde or ketone as a probe reaction, and evaluating the catalytic oxidation performance. The ternary LDHs thin film precursor is obtained on the aluminum substrate by the in-situ growth method, and the multi-element MMO thin film is obtained through high temperature calcination. The preparation method has the advantages that the prepared thin film catalyst is applied in catalytic oxidation of ethylbenzene, has the advantages of good stability, high catalytic efficiency, renewable recycling and the like, and has potential application prospects in petroleum industry catalysis.