High-resolution 1H and 13C nuclear magnetic resonance spectra are used to investigate the intermolecular interaction of polyester-polyurethanes with different contents of hard segments and different degrees of ionization. Because there are several kinds of hydrogen bonds, the hydrogen bonds play an important role in phase separation and physical properties. The higher the percentage of intermolecular hydrogen bonds, the greater are the tensile strength and strength at definite elongation. The interaction between 4,4′-methylene diphenyl diisocyanate and N-methyldiethanolamine is weak for the ES-33.4 series. Ionization does not change the percentage of intermolecular hydrogen bonds for the ES-33.4 series and ES-41 series, and ionization does not improve the physical properties and phase separation.