The interaction of solutes with β-cyclodextrin leads to apparent changes in their chemical properties, such as shifts in their absorption spectra and acid-base equilibrium. Formation of inclusion complexes between acid and/ or base forms of a compound with β-CD can change the amount of conditional acidity constant. The acidity constants of 2-(2H-benzo (d)(1,2,3)triazol-2-yl)phenol (CFM) in water and in the presence of varying amounts of β-cyclodextrin at 25 °C and an ionic strength of 0.1 M have been determined spectrophotometrically. To evaluate the pH-absorbance date, a resolution method based on the combination of soft- and hard-modeling is applied. The acidity constant of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program was applied for determination of acidity constant. The pKa value of CF is 8.50±0.10. The pKa value is decreased by increasing β-CD concentration.