▎ 摘　　要

NOVELTY - Preparing porous composite film comprises (a) dispersing polyvinylidene fluoride as a solute to N,N-dimethylformamide, stirring in a water bath at 85 degrees C to obtain a polyvinylidene fluoride/N,N-dimethylformyl solution, (b) dispersing the carbon nanotubes and graphene nanosheets in the polyvinylidene fluoride solution, ultrasonically processing, drying, adding to the polyvinylidene fluoride solution together with polyvinylpyrrolidone, ultrasonically processing to form carbon nanotube/grapheme/polyvinylidene fluoride mixed solution, (c) evenly applying the carbon nanotube/grapheme/polyvinylidene fluoride mixed solution on the glass plate and (d) immersing the carbon nanotube/grapheme/polyvinylidene fluoride film in a 50 degrees C water bath for 10 minutes to make the film fall off, placing the carbon nanotube/grapheme/polyvinylidene fluoride film in distilled water, sealing for 24 hours and drying to obtain a porous composite film. USE - The method is useful for preparing porous composite film. ADVANTAGE - The method utilizes an internal porous structure to reflect and scatter electromagnetic waves multiple times, thus improving the wave absorbing performance of the composite material.