Abstract: The directional solidification technique can obtain a specific columnar crystal structure, which has a very significant effect on optimizing the axial mechanical properties of the alloy. In addition, the convection phenomenon in the melt will also change the temperature field and concentration field at the front of the solid-liquid interface, which will affect the shape of the solid / liquid interface, and the influence on the properties of the alloy can not be ignored. Although the phase field method has more research on the micro dendrite growth morphology, the results of coupling the flow field into the phase field and exploring the micro dendrite morphology of directional solidification are still scarce. In this paper, the phase field model of coupled flow field is used to simulate the growth process of dendrites during directional solidification, and the effects of anisotropy coefficient and interface energy on the growth of directional solidification dendrites and the growth behavior of dendrites under forced convection are studied. For the numerical solution procedure, a uniform grid of finite difference method is used to discrete the governing equations. The combined solution of MAC algorithm and phase field discrete calculation are realized. When dealing with the coupling of micro velocity field and pressure field, the MAC algorithm was used for solving Navier-Stokes equation and pressure Poisson equation, the interlocked grid method was applied to deal with complex free interface. The results show that with the increase of the anisotropy coefficient, the growth rate of the dendrite tip increases, the radius of curvature decreases, and the solute concentration at the root of the dendrite decreases gradually. When anisotropy coefficient is the maximum of 0.065, the wall of dendrite is greatly affected by the anisotropy coefficient and tends to develop towards secondary dendrite;With the increase of the interface energy, the radius of curvature of the dendrite tip increases. When the interface energy is the maximum of 0.6, the solidification shows a flat interface advancing mode;Forced convection has a great influence on the growth direction of directional solidification dendrites. The directional solidification dendrites in the upstream direction are coarse and grow faster, and the phenomenon becomes more obvious with the increase of flow rate.In addition, by comparing the dendrite growth morphology observed by optical microscope experiments, it is found that the simulation results are in good agreement with the experimental results.