Three dimensional graphene/phenolic resin (3DGP) composites were synthesized via in-situ polymerization in graphene hydrogels (GHs). The water in the GH was perfectly replaced with resole resin due to the infiltration of resole resin into the GH and the evaporation of water from the GH by heating in the appropriate temperature. The 3DGP composite was obtained successfully by in-situ polymerization. The prepared composite can retain the complete 3D network structure to achieve good dispersion of graphene sheets forming 3D conducting network in polymer. The mechanical and electrical properties were measured, and the results showed that the composite possessed good electrical conductivity and compressive property. The compressive strength of 3DGP composite (441.11 MPa) increased by 14.24% compared with that of pure phenolic resin. In addition, the electrical conductivity of 3DGP composite reached 2.73 S/cm with a graphene loading of 2.15 wt% due to the 3D interconnected structure. (C) 2018 Elsevier B.V. All rights reserved.