The phase-field model based on the Tong and Bechemann model which couples the flow field was developed to simulate the effects of phase-field parameters on dendrite growth in microstructure of pure metal by the finite difference method （FDM）. The results show that the dendritic morphology obviously changes under the condition of convection, in which the branch of upper dendrite is the longest and that of down dendrite is the shortest and the length of the branch in horizontal direction is middle. The higher the undercooling rate is, the more development the side-branches in upper and in horizontal direction are; the larger the anisotropy parameters is, the thinner the branch of main dendrites is, and the smaller the second dendrite spacing is. In addition, the dendrite tip velocity is accelerated with the increase of convection velocity.