In order to conquer the brittle nature of bulk metallic glass(BMG),many efforts have been made for developing in situ composites.A review on the effect of in situ phase on the mechanical properties,such as morphology,size and preparation technology etc.is presented.The developments of BMG,going through compression,tension of small size specimen and large-size specimen,and becoming from brittle to plastic gradually.Furthermore,it is showed clearly that the semi-solid progressive solidification(SSPS) is an effective way to obtain large scale,defect-free in situ BMG composites with significant tensile ductility.