Abstract: Heteroatom doping engineering enables the modulation of metal-support interfacial interactions, which holds guiding significance for optimizing the performance of supported catalysts. In this study, natural coconut shells were used as the biomass carbon source, and a nitrogen-doped coconut shell carbon-supported PtNi alloy catalyst (PtNi/N-CSC) was prepared through high-temperature carbonization, nitridation, and solvothermal reduction processes. This research uncovers the regulatory mechanism of nitrogen doping on the interfacial interaction between the PtNi alloy and the coconut shell carbon support, as well as on the performance of the methanol oxidation reaction (MOR). Once highly electronegative nitrogen atoms are incorporated into the carbon lattice, they induce stronger charge transfer between PtNi and the carbon support. This strong metal-support interface effect can trigger the rearrangement of the electronic structure of Pt sites, resulting in an increased content of oxidized Pt^x+ species. This is beneficial for enhancing the adsorption energy of Pt sites toward *OH intermediates. In the methanol oxidation electrolyte (1 M KOH + 1 M CH₃OH), a large number of OH⁻ ions are adsorbed around Pt^x+ species. The CO_ads reaction intermediate generated at the Pt^x+ sites is further oxidized by *OH, which releases the Pt active sites. This process improves methanol oxidation activity, reaction kinetics, and CO tolerance. Compared with PtNi/CSC, PtNi/N-CSC exhibits a lower onset potential (0.29 V) and peak potential (0.72 V) for methanol oxidation, higher mass activity/specific activity (4.82 A mg_Pt⁻¹/8.23 mA cm_Pt⁻²), and stronger CO tolerance (6.99). The regulatory mechanism of electron transfer at the metal-support interface proposed in this study provides a new pathway for the design of supported catalysts.