The development of earth-abundant-metal-based electrocatalysts with high efficiency and long-term stability for hydrogen evolution reaction (HER) is crucial for the clean and renewable energy application. Herein, we report a molten-salt method to synthesize Co-doped CaMn₃O₆ (CMO) nanowires (NWs) as effective electrocatalyst for HER. The as-obtained CaMn_3−xCo_xO₆ (CMCO) exhibits a small onset overpotential of 70 mV, a required overpotential of 140 mV at a current density of 10 mA·cm⁻², a Tafel slope of 39 mV·dec⁻¹ in 0.1 M HClO₄, and a satisfying long-term stability. Experimental characterizations combined with density functional theory (DFT) calculations demonstrate that the obtained HER performance can be attributed to the Co-doping which altered CMO’s surface electronic structures and properties. Considering the simplicity of synthesis route and the abundance of the pertinent elements, the synthesized CMCO shows a promising prospect as a candidate for the development of earth-abundant, metal-based, and cost-effective electrocatalyst with superior HER activity. Our results also establish a strategy of rational design and construction of novel electrocatalyst toward HER by tailoring band structures of transition metal oxides (TMOs).