Co₃O₄ powder has a wide range of applications in the fields of catalysts, magnetic materials and electrochemistry. Especially after the 1990s, the demand for lithium ion battery industry has grown tremendously. The traditional wet preparation of Co₃O₄ powder cannot meet the requirements of the battery industry. Exploring suitable methods and theories for controlling particle size and morphology is of great significance for the preparation of battery-grade Co₃O₄ powder. CoCl₂ was used as the cobalt source, NH₄HCO₃ was used as the precipitant, and the precursor was prepared and further calcined to obtain Co₃O₄ powder. The results show that the molar ratio is the main factor affecting the precursor phase in the preparation of Co₃O₄ in CoCl₂-NH₄HCO₃ system. The suitable process conditions for the system are a molar ratio of NH₄HCO₃ to CoCl₂ of 4.5:1, a concentration of CoCl₂ of 13 g/L, a reaction temperature of 60°C, and a reaction time of 10 hours. The median diameter of Co₃O₄ prepared by the reaction conditions is about 9 μm.