Molecular dynamics simulations have been performed for the design of operating conditions of liquid-liquid interfacial crystallization and clarifying the crystallization mechanism. It was found that solute ions were dehydrated with diffusion of the hydration ions from solution to organic phase. There were a significant difference of the dehydration behaviour between NaCl solution/1-butanol and /2-butanone. Aggregated ions or clusters were formed by the dehydration near the solution/organic solvent interface. The number of cluster generation near NaCl solution/2-butanone interface was larger than that in the 1-butanol system. This difference originates in the interfacial structure in the NaCl solution/the each organic solvent interface.