The single-objective and multi-objective optimizations based on a multi-component standing-wavedesign were carried out for the tandem simulated-moving-bed (SMB) process for continuous-mode separation of galactotriose (G3) from crude galacto-oligosaccharides. This process (named ‘‘G3-SMB”) consisted of two subordinate SMB units. The results from the G3-SMB optimization showed that its two subordinate SMB units had a significant difference in column efficiency, which acted as a major factor for restricting the level of attainable throughput and deteriorating solvent usage. This problem could be overcome by allowing the use of different column lengths within the G3-SMB (called ‘‘S100 method), which was applied in a way that increased the column length of the subordinate SMB unit under the influence of column-efficiency limiting factor while decreasing the column length of the subordinate SMB unit with high column-efficiency. This method led to 32% increase in maximum achievable throughput and 37% reduction in solvent usage. It was also found that the adjustment of column configuration in each unit (called ”S2 method‘‘) was as effective in improving throughput as the S1 method, but less effective in reducing solvent usage than the S1 method. Finally, it was confirmed that the simultaneous use of the aforementioned S1 and S2 methods could create a synergy effect, thereby resulting in 74% increase in maximum achievable throughput and 39% reduction in solvent usage.