AbstractA Compressive test on Zr-based metallic glass was performed using a universal testing machine. The fracture process was recorded by high-speed video camera with a recording rate of 125,000 fps. The specimen was shear-fractured at 1.9GPa accompanied by the strong light emission. The fracture surface consisted of the brittle and vain-patterned surfaces. In addition, another compressive test was carried out in argon gas. Since light emission was not observed, it was evident that the light emission was a result of the oxidization of hot particles. In order to identify the beginning of the fracture, a splitting tensile test was carried out. Light emission began at the centre of the cross-section of a cylindrical specimen, and the crack was propagated in a direction of about forty-five degrees from the horizontal. The fracture criterion of Zr-based bulk metallic glass is not determined by the principal stress. The effect of the fraction of crystallization in Zr-based bulk metallic glass on light emission was also investigated using a specimen heat-treated at several temperatures. The relation between the fraction of crystallization and light emission was confirmed by the experimental analysis.