By coupling the micro-scale cellular automaton method proposed in author’s previous work with the momentum, mass and engery transport models, a multi-scale two-dimensional dendritic growth model (CA-FVM) is developed to investigate the columnar dendritic growth with forced convection. The effects of the forced convection on the columnar dendritic growth of Fe-0.82wt%C binary Fe-based alloy are investigated by the present mathematical model. The numerical results show that the forced convection of the molten melt has great influences on the columnar dendritic growth. The columnar dendrites near the inlet are significantly constrained by the enriched solute which is carried by the forced convection, and grow slowly. But the columnar dendrites far away from the inlet are affected by the forced convection slightly, and grow more fast. Additionally, with the increase of the force convection intensity, the influence of the forced convection on the columnar dendritic growth becomes more significant, and the asymmetric growth of columnar dendrite is intensified.