Graphene-based Split Ring Resonator (SRR) metamaterial is proposed with capacity of modulating transmitted THz waves based on the principle of surface-plasmon-polariton.The resonant strengths of plasmonic modes can be significantly enhanced by increasing the Fermi level of graphene, changing the gap distance of SRR or by stacking graphene layers, thus high modulation depth is achieved in both higher frequency region and lower frequency region. Modulation depth of 81% and 68% are achieved in the two regions, which can be further enhanced to 93% and 95%,provides a dynamical modulation based on controllable Fermi level of graphene. This graphene-based design paves the way forthe design of THz applications, such as modulators and absorbers.