Abstract: To evaluate the degradation mechanism of lycopene from red grapefruit,degradation kinetics of lycopene were investigated by constructing model systems of intrinsic factors in red grapefruit juice. The results indicated that lycopene degradation was significantly accelerated by ascorbic acid and sugars.However,β-carotene had a protective effect on the degradation of lycopene,which was more important comparing to the negative effect of ascorbic acid or sugars in the degradation of lycopene.Lycopene degradation was promoted by sugars which was closely related to temperature,and the degradation of lycopene in the presence of sugars followed complex reaction kinetics at comparatively higher temperature. The stimulative effects of sugars on lycopene degradation were according to the following descending order: glucose < sucrose < fructose.The degradation of lycopene in red grapefruit was promoted or protected by the synergy of different intrinsic factors,which provided the theoretical basis for researching and developing the red grapefruit products and functional food of lycopene.