The phase-field model based on the Tong and Beckermann model coupled with the flow field is used to simulate two-dimensional microstructural dendrite growth of metal by way of finite difference method. The effect of different convection velocities on metal dendritic crystal growth is studied. The result shows that the upstream and downstream dendritic crystal present asymetric pattern: the growth velocity of upstream is much fasfer than downstream. As the velocity of convection increases，actual supercooling of upstream dendritic crystal increases，the growth velocity of dendritic crystalis also speeded up. This is because of the bigger convection velocity leads to stronger flushing to the upstream dendritic crystal and the greater actual supercooling of upstream dendritic crystal，making the dendritic crystal to grow faster.