A kinetic Monte Carlo simulation is shown to investigate 3-dimensional growth of Ge on Si(111) substrate as monolayer of Pb atoms are pre-deposited as surfactant.We focus on Ge diffusion around edge of clusters.Effects of Ge diffusing around cluster edge,maximum diffusion steps for edge-diffusion and number of nearest neighbors on 3D growth mode are discussed.Coverage dependences of surface roughness are calculated to investigate growth mode.It shows that Ge edge-diffusion around clusters plays an important role on growth mode of 3D film growth.Effects of ES barrier on growth mode on Ge/Pb/Si(111) are explored.