We have performed molecular dynamics simulations to study the evolution of local atomic structure of the Cu50Zr50 metallic glass during glass formation. It was found that the coordination number of the Cu atoms mainly distribute from 10 to 12, whilst that of the Zr atoms ranges from 13 to 15. The structural analysis showed that the icosahedral-like and Frank–Kasper polyhedra are dominant in both the undercooled liquid and the glass, and Cu5Zr7 and Zr8Cu7 polyhedra are the major local structural units for the Cu- and Zr-centered clusters, respectively. Moreover, three typical medium-range orders constructed by icosahedral-like, Frank–Kasper, and Bernal polyhedra via the linkage of vertex-, edge-, face-, and intercrossed-shared atoms have been revealed in the metallic glass. The peculiar local structures and the connected complex medium-range ordering might be responsible for the high glass forming ability of the binary alloy due to their chemical and structural incompatibility with the primary competing crystalline phase.