A population dynamics-cellular automaton (PD-CA) model is developed to describe the microstructure formation in an inoculated Al alloys.The model involves the dynamics behaviors of the inoculated particles and the nucleation,initial spheri-cal growth of nuclei as well as the subsequent dendritic growth.The model was validated by using the experimental results for the Al-Cu alloys inoculated by Al-Ti-C refiner first,and then used to simulate the detailed solidification process in an inoculated Al-Cu alloy.The results indicate that the TiC is not stable in Al melt.The heterogeneous nucleation process consists of two stages:a very short initial stage dominated by the cooling rate and the later stage dominated by the number of the active TiC.It stops at the very moment the recalescence occurs.The average grains size d of the aluminum alloys inoculated by the Al-Ti-C refiner can be calculated by d(μm) =a·exp(t/60·ln(C0/w)) /(vcool.t)1/3w1/3+ b·ln t/Q·v1/2cool where Q is the growth restriction factor,C0 (％) is the initial solutes composition,w (％) is the additive amount of Al-Ti-C refiner.t (min) is the holding tem-perature time since the Al-Ti-C refiner is added into the melt.a and b are the constants.