Based on UV absorbance, a new and simple subtraction method was proposed for the calculation of the inclusion ratio, and it was proved to be equal in number to the classical molar ratio or phase solubility method. Using any kind of these three methods, the results always showed that the inclusion ratio of this complex was 11, which indicated that this kind of supramolecular complex was formed through an inclusion interaction between 1 host molecule (β-cyclodextrin) and 1 guest molecule (sorbic acid). Sincethe subtraction methodadopted a repetitive measurement and took the averaged, its result was more accurate than the molar ratio method; meanwhile, due to the advantage of less interference factors and especiallyno need of drawing a complicated phase diagram, its calculation process was much simpler than the phase solubility method.