The effects of gradient structure on the microstructure and properties of coated cemented carbides were researched with optical microscopy (OM), scanning electron microscopy (SEM), strength measurements, and cutting tests. It shows that vacuum sintering of WC-Ti(C, N)-TaC-Co cemented carbides results in the formation of a surface ductile zone. The ductile zone prevents crack propagation and leads to the increase of transverse rupture strength of the substrate. The impact resistance of coated gradient inserts was obviously improved on the basis of maintaining resistance to abrasion and the forming mechanism of the gradient structure was also analyzed. The effects of gradient structure on the microstructure and properties of coated cemented carbides were studied with optical microscopy (OM), scanning electron microscopy (SEM), strength measurements, and cutting tests. It shows that vacuum sintering of WC-Ti (C, N ) -TaC-Co cemented carbides results in the formation of a surface ductile zone. The ductile zone prevents crack propagation and leads to the increase of transverse rupture strength of the substrate. The impact resistance of coated gradient inserts was obviously improved on the basis of maintain resistance to abrasion and the forming mechanism of the gradient structure was also analyzed.