A molecular dynamics simulation is performed to investigate the icosahedron in Mg70Zn30 metallic glass during solidification at the cooling rate of 1 x 10(13) K/s. It is found that the 1551, 1541 and 1431 bondtypes are closely related to 13-atom icosahedron-like clusters. Two kinds of clusters are very similar to full icosahedron in geometry. The three clusters can transform into each other by changing one bond between a pair of outer atoms. One distorted icosahedron act as the intermediate between the two others. This work provides an insight into the glass formation in alloy from the cluster-level structural viewpoint and will shed light on developing more metallic glasses. (C) 2018 Elsevier B.V. All rights reserved.