Functionalized graphene is provided. The functionalized graphene is graphene onto whose surface one or more active molecules are grafted, the active molecule includes a plurality of terminal functional groups, and the plurality of terminal functional groups include at least two active functional groups. Because the active functional groups can chemically react with molecules in silicone oil, the functionalized graphene can evenly dissolve in the silicone oil, so that polyorganosiloxane prepared by using the functionalized graphene has good heat conduction performance. In addition, this application further provides a preparation method of the functionalized graphene and corresponding polyorganosiloxane.