Bulk metallic glasses (BMGs), due to the lack of long-range order and the absence of traditional defects such as dislocation and grain boundary, have a series of intriguing mechanical, physical and chemical properties.They have shown wide-spread potential applications in many fields as structural and functional materials.However, plastic flow of BMGs at room temperature is prone to be highly localized into nanoscale shear bands.The initiation and rapid propagation of shear band can induce catastrophic fracture with very limit ductility, impeding the further applications of BMGs.Hence, understanding fracture mechanism of BMGs is essential for seeking some possible ways to improve their room temperature ductility.