A series of polyether polyurethane (PU)-LaCl3 composites with different lanthanum contents were prepared. DSC results indicate that LaCl3 promotes phase transition behavior of the LaCl3/PU composites, which causes the endothermic peak at 11.58℃ to disappear. FTIR spectroscopy demonstrates that significant variation can be observed. The peak at 1 633 cm-1 attributed to carbonyl vibration and the peak at 3 311 cm-1 attributed to N—H stretching band moves to 1 647 cm-1 and 3 355 cm-1,respectively, when LaCl3 is introduced into the PU system. A new band (-200 cm-1) assigned to the La—O band was observed, and the far IR result provided a direct evidence of the coordination between La3+ ion and CO group of PU system.Key words:Modified polyurethane;Lanthanide;FTIR;DSC