Abstract: The orthogonal design and comprehensive evaluation methods were used to optimize the hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion technology of volatile oil from Thymus mongolicus and the aqueous solution stirring method was used to prepare the inclusion complex.The inclusion complex was characterized by fourier transform infrared (FT-IR) spectrum and the main chemical components change of volatile oil before and after being included by HP-β-CD were compared and analysed through gas chromatography-mass spectrometer (GC-MS) .The results showed that the optimal inclusion technology conditions were as follows:the ratio of volatile oil to HP-β-CD was 1:10 (mL:g) , the inclusion temperature and time was 30℃ for 2.5h, the concentration of HP-β-CD was 5%.The yield of inclusion complex and the utilization efficiency of volatile oil were 91.77% and 81.94% respectively under this optimal condition.The optimal inclusion technology conditions were reasonable, stable and feasible, the stabilities of the volatile oil were increased after being included by HP-β-CD.FT-IR and GC-MS analysis showed that the thymus volatile oil-HP-β-CD inclusion complex exhibitized some new physical characteristics and this mean the inclusion complex had been formed, the main chemical components of thymus volatile oil did not changed before and after being included by HP-β-CD, but the proportion of the components had been changed.HP-β-CD inclusion had slight effect on the chemical components and their proportion of the thymus volatile oil.