A novel AFC-based cationic waterborne polyurethane, very stable for long-term storage, was synthesized by importing the fluorescent agent 7-amino-4-(trifluoromethyl)coumarin (AFC) into the polyurethane chains. Structure of the WPU-AFC was confirmed by Fourier transform infrared spectroscopy (FTIR) and UV-visible absorption spectroscopy. The fluorescence intensity and average emulsion particle size for WPU-AFC were also determined. It was found that the fluorescence intensity of WPU-AFC decreased with the increasing temperature and was enhanced compared with that of AFC. The thermal stability of WPU-AFC improved compared with the WPU without AFC group.