FTIR spectroscopy and thermal analysis were applied to study the nylon 6-lithium salt systems. The DTA results show that lithium ions cause a significant reduction of the melting point of nylon-lithium salt samples. In addition, lithium salts can also prevent eae crystallization of molten nylon in the cooling process. Temperature-variable FTIR spectroscopy demonstrates that stronger hydrogen bonds form when nylon-lithium halide is molten. Such stronger hydrogen bonds in molten nylon lithium systems may account for the reduction of the melting point and delaying the crystallization of the amorphous nylon.