Designing earth-abundant and highly active hydrogen evolution reactions (HER) electrocatalysts is pivotal for developing renewable energies. Here, we report that Mn-doped NiSe2 nanosheets is successfully fabricated on carbon fiber cloth by solvothermal process and followed selenide reaction, showing excellent catalytic performance for electrochemical water splitting. Benefiting from the unique electronic property modified by Mn doping and nanosheets structures, the obtained electrodes only requires low overpotential of 86 mV to achieve the current density of 10 mA/cm(2) in acid solution. Moreover, the higher normalized exchange current densities manifest that Mn doping can improve the intrinsic activity of NiSe2. Furthermore, first-principle calculation results manifest that Mn doping can optimize the electronic structures to reduce hydrogen adsorption energy and consequently improve the HER active. This novel method is expected to provide new chances for developing efficient catalysts for energy conversion applications. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.