Sedimentation basin is an important component of every water treatment process. In order to improve the sedimentation efficiency (SE) of rectangular sedimentation basins, many researchers have proposed various methods. Among the suggested methods, the change of the geometry with installation of baffle in the basin floor is simple and completely economic. In this research, the hydraulic characteristics of the flow with various baffle configurations in the basin floor have been evaluated and the best geometry of the baffle has been presented. The agreement between numerical and experimental results was good. The results showed that the flow in the sedimentation basin is strongly influenced by the baffle. Also, the baffles installed with lower height and closer to the basin inlet and baffles with high height and far from the basin inlet have the greatest effect on the SE.