A simulation study has been carried out for the solidification process of liquid Ca50Zn50 alloy by using molecular dynamics method. The pair distribution function g(r) curves, bond-type index method, cluster-type index method (CTIM) and three-dimensional visualizing analysis method have been used to analyze the evolution properties of microstructures during the solidification process. The results show that, owing to the difference of atomic radius for Ca and Zn, the first peak of the total pair distribution function gtot(r) curve is split into three secondary peaks. With the decrease of temperature, the propability of Zn atoms being close to each other is increased obviously. In the system, the icosahedron basic cluster (12 0 12 0) consisting of 1551 bon-types plays a key role in forming amorphous structure. And the center atoms of basic clusters in the system are mainly the Zn atoms with smaller size. Most basic clusters with short-range order would be linked to each other in the manners of vertex-sharing(VS), edge-sha ring (ES) , face-sharing (FS) and intercross-sharing (IS) atoms. During the solidification process of forming amorphous state, most basic clusters would be linked with the manner of intercross-sharing (IS) atoms to form various larger clusters with different sizes, more tightness of connecting and more stability of structure.