A preliminary study demonstrated that CuS in the acid or basic slurry could be reduced to a certain extent by hydrogen in an autoclave. The reduction mechanisms in the two systems are probably different. The reduction of CuS in the basic slurry of pH 12.0 reached 92% under the hydrothermal conditions, such as 2.5MPa of partial hydrogen pressure, 220 degrees C for 3 h and adding 95% of stoichiometric ZnO.