NaCI crystals were precipitated on a liquid-liquid interface and control of the NaCI crystal shape could be realised. The interface between NaCl aqueous solution and 1-butanol, which show phase separation for small solubility of water and 1-butanol into each other, was used as a crystallization field. Asymmetric NaCl crystals could be created on the interface for changing of NaCl concentration due to mutual diffusion between two solvents. The particle size distribution could be controlled by changing the contact time between the NaCI solution and 1-butanol. The growth rate of NaCI crystals was varied with the concentration of the NaCl solution.