Many polyalcohols can change from one crystal structure to another in solid state at certain temperatures. A lot of papers reported their phase transition enthalpy, transition temperatures, and phase diagrams. This paper investigates the relation between transition enthalpy and hydrogen bond for the NPG (Neopentylglycol) and PE (Pentaerythritol) binary system on the basis of infrared spectrum experimental data and calorimetric results. It is shown that in the binary system some of the associated hydrogen bonds become weaker and are easier to break up. When temperature rises to a certain value, the hydrogen bonds, which retain in the course of phase transformation from the phase of NPG in PE to the plastic phase, will break up and form the second endothermal peak on the calorimetric curve. The number of retained hydrogen bonds is larger for the binary system NPG/PE with higher NPG concentration, and as a result, the corresponding enthalpy for the second endothermal peak is larger. While the influence of NPG on the retained hydrogen bonds is larger for binary system NPG/PE with higher NPG concentration, and the corresponding temperature of the second endothermal peak is lower.