Using an orthogonal design, i.e. the CoCl2 concentration, the current density, the temperature and the pH value as the factors, Ni-S-Co alloy was obtained through electrodeposition in a modified Watts bath by adding thiourea TU) and CoCl2 into the bath. The structure and morphology were determined by XRD and SEM. The electrochemical properties, including the, hydrogen evolution overvoltages eta (h.o.v.), the Tafel slope b, the exchange current density i(0) and the activation energy DeltaH* of amorphous Ni-S-Co cathode were measured. The effect of heat treatment under various temperatures on its structure and electrochemical proper-ties were determined. The results indicate that the structure of Ni-S-Co alloy obtained under the optimum conditions is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni-S electrode due to the higher sulfur content in such electrode, and heat treatment is harmful to its electrochemical activity. (C) 2003 Published by Elsevier Ltd on behalf of the International Association for Hydrogen Energy.