In this paper, we have theoretically demonstrated a graphene-mediated near-field radiative thermal modulator based on doped silicon-graphene-doped silicon three-slab configuration. The near-field photon tunneling between the doped silicon emitter and receiver is modulated by changing chemical potential of graphene sheet and the separation distance between the sheet and the emitter. The near-field three-body theory built on fluctuational electrodynamics is used to calculate total radiative heat flux, which could be modulated in a range of 10-70 kW/m2 with different setup for graphene chemical potential and its position. The underlying mechanismis illustrated as varied coupling behavior of surface plasmon polaritons between doped silicon and graphene sheet. Several dimensionless factors such as normalized heat flux, sensitivity factor and switching factor are also introduced for comprehensive analysis of the performance of modulation effect. The results obtained here will trigger a new way for near-field active thermal management between bulk materials utilizing suspended 2-D materials.