The essence of oxidation wear machanism of cenmented carbide tool was studied based on thermodynamics.Standard Gibbs free energy of possible reactions in cutting process at dif-ferent temperature was calculated using substance Gibbs free energy function methods,and the se-quence of reaction possibility order was researched as well as characteristics of every reaction.Theo-retical calculation shows that WO_3,Co_3O_4,TiO_2 and CoWO_4 are the main resultants,which are proved with the experiment results.