The invention discloses a preparation method for a Pt / ITO (Indium Tin Oxide) electrode of efficient electro-catalysis ammonia oxidate. The method comprises the following steps: step 1, preparing a working electrode: (a), cleaning ITO, (b), connecting a conducting wire with the conductive surface of the ITO cleaned in step (a) and packaging to obtain the working electrode; steps 2, connecting a Pt counter electrode, a saturated calomel reference electrode, the working electrode and electrolyte to form a loop so as to constitute a three-electrode system, wherein the electrolyte is a mixture of H2PtCl6 solution and HCl solution; and step 3, connecting the three-electrode system into an electrochemical workstation for electrodeposition. According to the invention, after chloride ions are injected into electroplating solution, the diameters of Pt prills obtained through electrodeposition can be reduced effectively, so that nanosheet-shaped particles can be obtained, and meanwhile, the dispersivity of the prills on the surface of ITO, the catalysis efficiency of Pt and the utilization ratio of Pt can be improved. The preparation method has the advantages of simple procedure, easiness in operation, low cost, environmental friendliness and obvious effect and has better properties when being compared with the current commercial catalysis electrode.