A series of boron-doped graphene-supported Pt (Pt/BG) nanosheets were designed and synthesized using a one-step facile hydrothermal method. ICP, XPS, and TPD results confirmed boron atoms were successfully embedded into graphene matrix. Selective catalytic reduction of nitric oxide with hydrogen (H2-SCR) was tested over Pt/BG catalysts. The multi-roles of doped-boron were investigated by Raman, BET, CO-Chemisorption, H2-TPD, XPS, and NO-TPD. Boron doping led to higher dispersion and smaller size of Pt nanoparticles, facilitated hydrogen spillover, promoted more metallic Pt formation, and increased both H2 and NO chemisorption, which were attributed to enhanced Pt nucleation rate over doped-boron, electron donation from boron to Pt, and extra chemisorption sites. The reaction performance (conversion 94.7%, selectivity 90.3%, and TOF 0.092 s-1) were greatly promoted attributing to a bifunctional catalytic mechanism. This work paves a way to modify structure and tune chemisorption ability of graphene-based catalysts, and provides novel insights for designing high performance catalyst.