The invention discloses a preparation method of a silver/graphene/zinc oxide composite material capable of degrading formaldehyde. The preparation method is characterized by comprising the following steps: (1) preparing ZnO nanoparticles; (2) uniformly dispersing Ag nanoparticles on the ZnO nanoparticles through physical vapor deposition; embedding graphene into an Ag/ZnO nano composite structure in a chemical vapor deposition manner to form Ag/graphene/ZnO composite nanoparticles; furthermore, mixing the Ag/graphene/ZnO composite nanoparticles prepared by step (2) with coconut shell active carbon and polyethylene; sintering to obtain sintered active carbon particles rich in Ag/graphene/ZnO composite nanoparticles. According to the Ag/graphene/ZnO composite material prepared by the preparation method, the technical bottleneck that an existing product only can have a photocatalysis effect under ultraviolet light is broken through a surface plasma resonance effect of the silver nanoparticles under visible light; the Ag/graphene/ZnO composite material has the advantages of good photocatalysis effect, simplicity and high efficiency.