A numerical model was developed for the simulation of microstructure evolution during the solidification of Nb-Si eutectic alloy. In this model, the cellular automaton method was used to simulate the eutectic growth of Nb solid solution and Nb3Si intermetallics. Diffusion in liquid, mass conservation at the solid/liquid interface and local equilibrium at the solid/liquid interface with consideration of curvature undercooling were solved to determine the positions of the Nb/liquid and Nb3Si/liquid interfaces. In the alloy with eutectic composition of 0.18at%Nb, irregular eutectic growth morphology was observed in relatively lower undercooling region. On the other hand, in higher undercooling region over 50K, dendrite morphology of Nb3Si was observed. An alloy with hypo-eutectic composition, cell and dendrite morphology were observed in lower undercooling region, while coupling eutectic morphology was formed in higher undercooling region over 25K.The growth velocity of the coupling growth increased with increase in the degree of undercooling of melt.