The invention discloses an in-situ polymerization method of graphene/vinyl chloride. By using a mechanical ultrasonic dispersion and microemulsion dispersant system, an in-situ polymerization grade graphene microemulsion is obtained; the graphene microemulsion is added into a vinyl chloride suspension polymerization system, and vinyl chloride monomers and graphene are subjected to in-situ polymerization, so that graphene/polyvinyl chloride resin subjected to in-situ polymerization is obtained. Observations implemented by using a transmission electron microscopy (TEM) show that graphene is arranged in a nanoscale monolayer dispersion mode in a polyvinyl chloride resin matrix, so that the thermal ageing properties and mechanical properties of the resin are significantly improved.