Abstract: The aim of the study was to optimize the preparation process of cinnamon oil- β- cyclodextrin microcapsules. Microcapsules were prepared by ultrasonic method and on the basis of single factor tests,orthogonal tests were carried out to optimize the preparation conditions with embedding rate as the appraisement index.The results showed that the optimized conditions were established as follows: ratio of cinnamon oil to β-cyclodextrin was 1 ∶ 8( mass ratio),ultrasonic power 231 W,temperature 40 ℃,time 50 min and under these conditions,the embedding rate and the average diameter of the capsules were 38.17% and 456.7 nm,respectively.Amplification test results showed that the amount of cinnamon oil increasing by 4 times caused only 3.83%reduction on embedding rate which suggesting the stability of the preparation conditions.Fourier transform infrared spectroscopy( FTIR) and differential scanning calorimetry( DSC) demonstrated the formation of the microcapsules.Thermogravimetric analysis( TGA) showed that cinnamon oil had a strong volatility and the remaining mass was only 0.15% after 218.0 ℃,yet the cinnamon oil embedded began to loss mass after 210.0 ℃ which indicating the improvement of the thermal stability of cinnamon oil. The main constituents of cinnamon oil did not change significantly before and after embedding proved by thin- layer chromatography( TLC). There was no significant difference on embedding rate of microcapsules prepared by ultrasonic and saturated aqueous methods,while microcapsules prepared by ultrasonic method contained higher drug loading with 0.71% than saturated aqueous solution method. Meanwhile,the microcapsules prepared by ultrasonic method exhibited higher embedding rate( increasing 4.21%),showed greater yield( enhancing 3.58%) and contained higher drug loading( improving2.60%) than kneading method,respectively. Ultrasonic method is a simple and efficient method for preparing cinnamon oil-β- cyclodextrin nanocapsules with high quality.