The inclusion complex formation of tanshinone IIA(Tan IIA)with hydroxypropyl-β-cyclodextrin(HPCD)was studied by using phase solubility method,and the formation constant for tanshinone IIA-HPCD- dextrin was determined.The effect of temperature on the reaction was studied through thermodynamics,and the changes inentropy,enthalpy,and free energy of the reaction were calculated.The molecular modeling provided further evidence for the formation of the inclusion complexes.Stable inclusion complex in solid state was characterized by IR spectra.