In order to investigate the thermal decomposition behaviors of cobalt carbonate and character inheritance of products, the predominance area diagrams of Co—C—O and the decomposition balances of cobalt carbonate in different atmospheres were studied. It was concluded that CoCO3 was mainly decomposed into CoO in the oxygen-free atmosphere and above 200 ℃. In the oxygen atmosphere, the oxidation decomposition reaction of CoCO3 was very easy to occur to generate Co3O4, while it would decompose into CoO and O2 at a temperature higher than 930 ℃, and the decomposition temperature decreased with the increasing of oxygen partial pressure. The thermodynamic analysis conclusion was confirmed by the verification tests, and there was a character hereditary of the decomposed products in the thermal decomposition process. The shape of Co3O4 depended on that of CoCO3. The increase of decomposition temperature led to the agglomeration and contraction of decomposition products and the particle size increasing of CoO.