Abstract: Graphene modified epoxy resin, which can be used widely in the microelectronic device area, has attracted a great deal attention due to its excellent thermal conductivity and mechanical strength. However, the reported thermal conductivities of thermal interface composite (TIMs) from different research groups shows obvious discrepancy even if the adopted mass fraction of graphene is identical. After research, we found that the reduction degree is closely related to the thermal performance of resulting TIMs. Thereby, it is difficult to evaluate the RGO acting as conductive filler under uniform standard. In this study, 3D graphene network was employed as the conductive filler to prepare a series thermal interface composites with epoxy resin. The influence from mass fraction of adopted 3D graphene network on the thermal conductivity of resulting thermal interface composites was studied, and the influences on the thermal performance stability under high temperature and mechanical properties were revealed. The findings are useful to build a completed evaluation system for estimate the ability of graphene using as conductive filler.