Ni-S-Co alloy was prepared by electrodeposition in a modified Watts bath with addition of thiourea (TU) and CoCl2. The structure and morphology were determined by XRD and SEM respectively. The contents of S and Co were measured by EPMA. The electrochemical properties of the alloy used as a cathode, including hydrogen evolution overvoltage n (h.o.v.), Tafel slope b and exchange current density f were measured. The HER mechanism and steady-state behavior of Ni-S-Co alloy in alkaline media were also investigated. The results indicate that the structure of Ni-S-Co alloy obtained is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni-S and Ni-S(La) electrodes. The HER on Ni-S-Co alloy cathode is a fast Volmer reaction following a slow Heyrovsky reaction, and the high electrocatalytic HER property is mainly due to the large amount of adsorbed H atoms.