This Finnis-Sinclair potential is suitable for molecular dynamics (MD) simulation of solidification of Al3Sm alloy. The MD simulation showed a layer-by-layer solid-liquid interface (SLI) motion mechanism in the [001] direction. The SLI migration seems to be satisfactorily described by Wilson-Frenkel theory in the temperature interval from 0.7Tm to Tm. It was found that the SLI passes an atomic plane as soon as the Sm sublattice is formed while the Al sublattice keeps forming for a while after that, and high Al diffusivity is observed in the solid phase. Those unsettled Al atoms trapped in solid phase will leave vacancies and form defects.