Many different configurations of the inlet and outlet in the risers have been studied. According to their effects on the structure of gas-solids two-phase flow, the inlet and outlet effects can be classified as the restriction on the solids circulation flow and the arrangement of open area. Both of them influence the axial and radial distributions of bed voidage seriously. Since hydrodynamics at the bottom and top sections in risers depend strongly on the inlet and outlet configurations, the effects of inlet and outlet must be considered carefully when modeling riser flows. It is important to design the riser configurations at the inlet and outlet to meet overall processes design requirements.