The dynamic evolution of grain growth in the process of aluminum casting and the impact of different casting conditions on the grain growth were simulated by using the Cellular Automation(CA) method in this paper. The simplified binary alloy was used to simulate the growth of the grain in the undercooled melt, Finite Difference Method (FDM) combined with relative motion was used, and dynamic evolution of microstructures in the process of aluminum twin-roll casting was achieved. Visual Fortran programming language was adopted to calculate and realize the image post-processing. based on the growth of the grain in the undercooled melt, the impact of the undercooling triggered by cooling and the casting speed on aluminum strip in the casting process was simulated. The results indicate that, in the condition of a certain nucleation rate, as the cooling intensity increases, bigger the grain is, which provides a basis for optimizing the twin-roll casting process parameters.