The mobility of atoms at a Pb solid-melt interface has been studied using molecular dynamics simulation. Three cooperative diffusive mechanisms were directly observed: immobilization, vacancy diffusion and desorption-mediated jumps. We hold that the in-plane structural ordering and desorption-mediated diffusion mechanism result in the formation and movement of vacancies at the solid-melt interfaces. A one-dimensional random walk model was proposed to describe the atomic movement at the solid-meltinterfaces. In addition, we suggested that in-plane structural ordering plays an important role in the diffusion process. (C) 2015 Elsevier B.V. All rights reserved.