The invention discloses a manufacturing method of an electrothermal film. The manufacturing method comprises the following steps of A, preparing an electrothermal film treatment solution which comprises tin tetrachloride, titanium trichloride, antimony trichloride, calcium chloride, chromic oxide, manganese dioxide, nickel sesquioxide, isopropanol, alcohol and water, B, masking a substrate, C, heating the substrate to be 400-700 DEG C and then spraying the electrothermal film treatment solution on the substrate by a spray gun to form a semifinished electrothermal film, D, annealing the semifinished electrothermal film, and E, coating silver oxide paste on the surfaces of the two ends of the annealed semifinished electrothermal film, loading the semifinished electrothermal film into an electrode oven, baking and fusing the semifinished electrothermal film to form a whole, and obtaining the finished electrothermal film. The manufacturing method has the advantages that the stability of the electrothermal film is improved by adding antimony; the temperature resistance of the electrothermal film is improved by adding titanium; the infrared emitting ability of the electrothermal film is improved by adding nickel and manganese; and an adhesive force between the electrothermal film treatment solution and the substrate is increased by adding isopropanol.