Abstract: In this research,octenyl succinate anhydride modified starch( OSA starch) was chosen as emulsifier to prepare a nanoemulsion system to contain lycopene and the emulsifying characteristics of OSA starch were determined.The result showed that OSA starch showed an optimal emulsifying characteristics when dissolved at 70 ℃ with 30%( w/w) concentration.Nanoemulsions using OSA modified starch as emulsifier were prepared by high-pressure homogenization with particle size of about 120 nm,where the rate of oil to aqueous phase was 1∶ 9( w/w),lycopene( 0.1%,w/w) in MCT and the lycopene retention was 63%.After 30 days of storage at room temperature,the particle sizes was increased to 160 nm with the growth of less than34%,and there was no obvious phase separation for the sample,indicating that OSA modified starch was a suitable emulsifier for the preparation of nanoemulsions.