Abstract：A study of the weak interactions of acetonitrile-water-sodium perchlorate mixtures has been performed using attenuated total reflection two-dimensional FTIR spectroscopy (ATR-2D-FTIR). The results indicate that CH3 and OH in the mixtures have some weak interactions with each other. The inorganic salts, sodium perchlorate, disbond hydrogen-bonded structure of water. Some interactions have been found between ions of sodium perchlorate and water molecules. Cations of Na＋ are combined with hydrogen- bonded water. Inorganic salts play an important role in changing the microstructure of the mixtures.