The initiation and evolution of shear bands in Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass tensile samples has been investigated in situ by scanning electron microscopy. The initial shear band originates from the highest stressed area, and does not propagate during further tension, which is attributed to the weakening of the stress field in front of the shear band tip, possibly caused by atomic rearrangement and local temperature rise. As a result, multiple shear bands occur in sequence with gradually increased length and offset. This result is due to the fact that the stress in front of the tip of the initial shear band does not concentrate again during further tension above the shear yield strength. Numerical analysis was carried out to investigate the stress distribution under tension, suggesting that the maximum pressure-dependent shear stress criterion overestimates the yield strength, while the shear plane criterion describes the conditions for the formation of shear bands well.