A method for preparing a modified polypropylene film, the modified polypropylene film comprising a polypropylene film; and, an oxide layer and/or nitride layer, each of which has a thickness of 20-500 nm, on a surface of the polypropylene film; the method comprising: depositing the oxide layer or nitride layer on a surface of the polypropylene film by an Atomic Layer Deposition (ALD) process to obtain the modified polypropylene film; wherein the step of depositing the oxide layer or nitride layer comprises: placing the polypropylene film in an ALD reaction chamber; vacuumizing; heating up; introducing a carrier gas; and, passing at least two precursors into the reaction chamber alternately for reaction, resulting in the modified polypropylene film; wherein the precursors comprise a precursor for providing a metal element or Si, and a precursor for providing an oxygen or nitrogen element.