In reactor research, the safety of the reactor plays an important role. Besides the experiment research, computational simulation can also provide important information about the behavior of materials inside the reactor core. The Moving Particle Semi-Implicit (MPS) method assists in providing information about the reactor material computationally. In this study, the stratification process of several materials, i.e. the melts of PbBi, PbLi, and Pb in combination with Al, have been investigated by simulation. The time to achieve stratified conditions for each material has been obtained where each paired material needs 0.5 seconds to reach the stratified condition. It is also obtained that the Pb-Al is the fastest in reaching the stratified condition among the other used materials.