Abstract: Solution spray-oxidation as a novel method was developed to prepare cobalt oxide powders. Engineering tests were conducted to investigate the effects of some main factors such as temperature, atomization pressure and CoCl₂ solution flow rate on the conversion efficiency of cobalt oxide, the particle size and the apparent density of the powders. The optimum conditions to obtain cobalt oxide were determined as follows:temperature 750℃, solution concentration 120 g·L^-l, air pressure 0.23 MPa, solution pressure 0.15 MPa, solution flow rate 40 L·h^-1, heat treatment temperature 750℃, and heat treatment time 2 h. Under these conditions, the conversion efficiency of cobalt oxide is 100%, the content of cobalt in the product is 73.04%, the apparent density of the powder is 0.48 g·cm^-3, and the average particle size of the powder is 7.61 μm. It is shown by the engineering test results that the solution spray-oxidation method is available for Co₃O₄ preparation and the process is simple, fast and environmental friendly.