The invention provides a preparation method and application of a nano-modified PTFE and polyester-based composite film for preventing fan blades from icing. The method includes the steps of PTFE film modification, lamination complexing and photo-crosslinked adhesive application. A modifier is prepared from antimony-doped tin oxide nano-crystals, nano-titanium dioxide, nano-silicon carbide, an organic fluorine waterproofing agent and pentaerythritol tri-(3-aziridinyl)-propionate; in lamination complexing, a bonding complexing agent is prepared from 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, vinyl acetate, ethyl carbamate, alpha-linolenic acid, (2)ethoxylated bisphenol A dimethacrylate, trimethylolpropane triacrylate and benzoyl peroxide; a photo-crosslinked adhesive is prepared from a poly[butyl acrylate-glycidyl methacrylate-n-butoxy methacrylamide]copolymer, vinyl acetate, butyl acrylate, an acrylate derivative, a photoinitiator and dimethylformamide. The method and the composite film solve the non-adhesion problem that a PTFE film can not be pasted on the surfaces of fan blades with an adhesive directly.