The invention relates to the nano polymer composite material technical field, and relates to a method for in-situ suspension polymerization preparation of a polyvinyl chloride/graphene composite material. With adopting of a reverse feeding way, an oil-soluble graphene powder and a vinyl chloride monomer or a vinyl chloride and functional monomer mixture are mixed and then polymerized, so that the compatibility and interaction problems between the graphene powder and the polymer matrix are solved, and the problems in the prior art that graphene is dispersed unevenly and polyvinyl chloride is incompletely coated with graphene are overcome; at the same time, compared with thermal stability and mechanical properties of conventional graphene/polyvinyl chloride resin and conventional polyvinyl chloride resin, the thermal stability and mechanical properties of the obtained polyvinyl chloride/graphene composite material are all improved, therefore, the obtained polyvinyl chloride/graphene composite material is indicated to have superior performance and is suitable for industrialized production.