Surface plasmon-polaritons (SPPs)-based waveguides, especially hybrid plasmonic nanowires, which have attracted extensive interests due to easy fabrication, high transmittance, subwavelength mode confinement and long propagation distance, are appropriate platforms for enhancing the interaction with graphene. Considering that graphene is a two-dimensional (2D) material with surface conductivity, it is important to enhance the in-plane electrical components parallel to graphene. Here, we propose a tunable graphene optical modulator based on arrayed hybrid plasmonic nanowires, utilizing strong subwavelength confinement of gap-surface plasmonic modes (GSPMs) and near-field coupling in the periodic metasurface structure to enhance effective light-matter interactions. The modulator has a typical modulation depth (MD) of 4.7 dB/μm, insertion loss (IL) of 0.045 dB/μm, and a broadband response. The modulation performance can be further optimized, achieving MD of 16.7 dB/μm and IL of 0.17 dB/μm. Moreover, with the optimized modulator, the 3 dB bandwidth can reach 200 GHz. The energy consumption of modulator is about 0.86 fJ/bit. Our design exhibits fascinating modulation performance, fabrication compatibility and integration potential. It may inspire the schematic designs of graphene-based plasmonic modulator and pave a way to the application of 2D materials-involved optoelectronic devices.