Efficient hydrogen evolution reaction (HER) over noble-metal-free electrocatalysts provides one of the most promising pathways to face the energy crisis. Herein, facile cobalt-doping based on Co-modified MoOx-amine precursors is developed to optimize the electrochemical HER over Mo2C nanowires. The effective Co-doping into Mo2C crystal structure increases the electron density around Fermi level, resulting in the reduced strength of Mo-H for facilitated HER kinetics. As expected, the Co-Mo2C nanowires with an optimal Co/Mo ratio of 0.020 display a low overpotential ((10) = 140 and 118 mV for reaching a current density of -10 mA cm(-2); (100) = 200 and 195 mV for reaching a current density of -100 mA cm(-2)), a small Tafel slope (39 and 44 mV dec(-1)), and a low onset overpotential (40 and 25 mV) in 0.5 m H2SO4 and 1.0 m KOH, respectively. This work highlights a feasible strategy to explore efficient electrocatalysts via engineering on composition and nanostructure.