Three metallic glasses Zr41.25Ti13.75Ni10Cu12.5Be22.5, Ce68Al10Cu20Co2 and Fe41Co7Cr15Mo14Y2C15B6(all in at.%), were compressed experimentally, and the fractured samples were investigated by scanning electron microscope. It was found that they exhibit different fracture modes. In three-point bending tests of the three pre-notched metallic glass samples, a digital speckle technique is adopted to in-situ observe the elastic strain field evolution in front of the crack tip. Accroding to the yield criterion of metallic glasses, the mechanism of different fracture processes in metallic glasses with various fracture toughnesses are elucidated.