The invention discloses a high-temperature-resistant modified polypropylene film, and a preparation method and application thereof. The modified polypropylene film comprises a polypropylene film and an oxide layer and/or a nitride layer on the surface of the polypropylene film; the thickness of the oxide layer or the nitride layer is 20-500nm. The thermal stability and high-temperature voltage resistance of the polypropylene film can be obviously improved by depositing an oxide layer or a nitride layer with proper thickness on the surface of the polypropylene film by using the ALD technology. The modified polypropylene film has high temperature resistance, such as 150 ℃, has extremely small deformation amount at high temperature, can bear high breakdown voltage at high temperature, such as 580kV/mm at 140 ℃, and has wide application in the field of electronic products with high temperature requirements, such as capacitors.