Multiple electronic structure modification is propitious for constructing strong metal–support interaction and then improving the electrocatalytic activity of supported catalysts, yet remains a great challenge due to the lack of facile protocols. Herein, we report a CoIr alloy supported on two dimensional (2D) graphitic-N doped carbon (CoIr@CN) through a one-step annealing process from an Ir-doped 2D Co-MOF, which exhibits a remarkably reduced Ir loading (2.69 wt%) and enhanced electrocatalytic activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Ir plays an essential role of optimizing the properties of metal nanoparticles and simultaneously effecting the calcining process to adjust the N-doping structure, eventually modulating the synergetic effect between alloy nanoparticles and the N-doped carbon support. Owing to the positive effect of such multiple electronic structure optimization, the electron transfer between alloy nanoparticles and N-doped carbon is promoted to enable more moderate adsorption energies of reaction intermediates in both the OER and HER. Impressively, CoIr@CN exhibits a low OER/HER overpotential of 269 mV/70 mV to achieve a current density of 10 mA cm⁻² in 1.0 M KOH, and 25 mV in 0.5 M H₂SO₄ for HER, as well as a negligible decay of catalytic activity after long-term stability measurements for OER/HER. This study offers an effective way for designing strong metal–support interaction through multiple electronic structure modification, which effectively improves the OER/HER performance of supported catalysts.