Abstract: By means of constant temperature and constant volume molecular dynamics, square displacement and radial distribution function, the microstructure, existence form and distribution of Sn in Cu substrate were studied, and the experimental test was performed. The results show that Sn solid soluted in Cu substrate and probably formed to intermediate phase of Cu6Sn5, but the agglomerate phenomena for Sn in Cu substrate had no appeared. The accuracy of the model dynamics simulation were tested by the experimental results.