Combined with Jackson interface theory, molecular dynamics simulation (MD) and density functional theory (DFT), the solid-liquid interface morphology during the growth of silicon crystals (100) and (111) planes was studied, including changes in interface free energy, structure change and growth position adsorption energy. According to the calculation of Jackson interface theory, it is found that the Gibbs free energy of (100) interface crystal phase atom and fluid phase atom reaches a minimum value when they account for about 50% of the surface, while (111) interface reaches a minimum value when they account for about 0% or 100% of the surface, which indicates that (100) plane tends to rough surface and (111) plane tends to smooth surface when the thermodynamics is in equilibrium. Molecular dynamics simulations show that as growth progresses, the initial smooth solid-liquid interface at the (100) plane will gradually transform into a rough interface, while the (111) plane will always maintain a smooth interface growth. And during the growth process, the growth rate of the (100) plane is significantly higher than that of the (111) plane, because the (100) plane growth is always rough surface. DFT calculation shows that the adsorption energy of all growth on (100) plane is close, and continuous growth can be achieved, while the adsorption energy of (111) surface is stored in the obvious difference, the growth atoms need to be adsorbed on the steps to carry out layered growth.