A new feed mode for simulated moving bed (SMB) is proposed. The solution out of zone II flows into a tank to dissolve the solid raw materials and is then fed into zone III. The feasibility of the new feed mode was examined with a model SMB operation. The results showed that this mode could effectively separate mixtures. As the raw materials are dissolved with the solution from zone II, the solvent consumption is reduced significantly in comparsion with the traditional SMB operations; whereas the productivities and purities change insignificantly. When the flow rates of raffinate and extract stream are similar, the concentration plateaus of two solutes in column have similar and suitable heights, otherwise an overly high concentration could cause the solutes to be crystalized and plug the column. The volume of solution tank showed an insignificant effect on the separation. Increasing the tank volume can make a smooth change of concentrations of solutes in the tank, which is beneficial to the operation.