Abstract: Molecular dynamics with embedded atom method was used for research regularity of hetero-epitaxial initial-growth evolving with island size in Ti/Fe(001) system. The results show that the epitaxial island critical size which determinates growth model exists in the process of Ti growing on Fe(001) surface, the atoms on the edge of island decrease system energy through upward transportation while epitaxial island size is above the critical value. The interface mesoscopic mismatch and adhesion energy between epitaxial island and substrate decrease with the growth of epitaxial island and crystal structure mismatch lead the average bond of island to be less than that of Fe substrate. The variation of epitaxial island average bond will affect micro-morphology, stress and strain condition of epitaxial island and substrate.