Molecular dynamics simulations are used to investigate the surface melting processes of three low-index surfaces of aluminum. We find that the surface melting is anisotropic for different surfaces by analyzing the variation of the microstructures during melting. Although （001） and （111） surfaces can both sustain overheating, the microstructures of them are different. There is a thin disordered quasi-liquid film on （001） surface when overheated while the （111） surface is crystalline. It is surprising that the melted （001） surface can be overheated. The velocity of melting is calculated for all the surfaces at different temperatures, and the melting point is extrapolated to be 950 K±9 K which agrees with the experimental data of 9335 K.