Abstract: A simulation study on the transition properties of microstructures in the solidification process of liquid metal Al is performed using the molecular dynamics method. It is found that in the range of temperature of 943~50 K, the relative numbers of 1551 bonds related to the icosahedral structure increase remarkably, which play a critical role in the variation of structural configurations during the rapid cooling process. It is also demonstrated that with the decrease of temperature, the degree of the order of the system increases, while, the degree of disorder of the system decreases.