The invention discloses a preparation method of cobalt oxide for a lithium battery, which comprises the following steps: mixing a stabilizing agent and a cobalt salt solution to obtain a solution A, adding a precipitating agent into the solution A to be precipitated, and obtaining cobalt oxide by the purification and oxidization of precipitate, wherein the stabilizing agent is at least one of oxalic acid and sulfosalicylic acid. The invention also discloses the cobalt oxide for the lithium battery which is prepared by the method. The invention has the beneficial effects that: (1) the stability of process operation in the preparation process is good, and carbon dioxide, nitrogen compounds and other substances harmful to the environment are not emitted in the production process; (2) the cobalt oxide obtained by the preparation method has regular lattice and unit cell, and finished product atoms, ions and molecules obtained by further deep processing have uniform extraction and insertion, thereby improving the electrochemical properties, photochemical properties and structural stability of the corresponding products.