The invention discloses a preparation method of a PVDF-Ag/AgBr/g-C3N4-BiOCl(001) composite membrane and belongs to the technical field of photocatalysts. Active ingredients of the composite membrane are Ag/AgBr/g-C3N4 and BiOCl(001), and a structure of the composite membrane is that Ag/AgBr/g-C3N4 and BiOCl(001) are distributed in a PVDF matrix. The preparation method is characterized in that firstly BiOCl(001) is used for doping PVDF, then an Ag/AgBr/g-C3N4 nanocomposite is introduced, the SPR effect of precious metal is utilized to be combined with a crystal plane engineering technology, and separation and transmission of photo-induced electrons are optimized, so that the catalytic activity is improved. For MO degradation reaction, when the composite membrane is used as a photocatalyst, a 30W LED lamp is taken as a light source, and the degradation rate of MO reaches 92% when the irradiation time is 120 minutes.