Abstract: By closely combining with the quality inspecting work in the industrial production of WC-Co cemented carbide and using the comprehensive functions Of OLYMPUS PMG3 type optical microscope and JCXA-733 type electron probe microanalyser,this paper has more all-roundly observed and analysed the fractrur behaviour and pathway of fracture and the orient extension of fracture source, the pathway of craze,the composition of pore and impurity and the surrounding structure of the alloy. The important structural factors of influencing fracture strength and fracture mechanism of the alloy have been illustrated.