In this work, Graphene/SnO2 composites were prepared by hydrothermal synthesis method to modificate the surface of grapheme, which were then used to prepare Graphene/SnO2/Cu through powder metallurgy. Many different methods were used to measure and analysis the composites’ microstructure and properties. The results reveal that SnO2 nano-particles absorbing on the surface of grapheme will not shed during the process of preparation. At the same time, SnO2 particles can inhibit aggregation of graphene, and improve the composites’ density, hardness and thermal conductivity. Graphene/SnO₂/Cu composites’ density is 91.0%, hardness is 166 HBW, and thermal conductivity is 139 W/ (m℃), which are more higher than Graphene/Cu composites. Graphene/SnO2/Cu composites’ bonding at the interface is well, with no crack or interfacial reaction. There are three main reasons that lead to the decrease of electrical conductivity of the composites, namely edge dislocation and deformation twin of copper matrix and SnO2 nano-particles on graphene’s surface.