The contents of sugars and the activities of sucrosemetabolizing enzymes in three different color fruits of Lycium were determined during five fruit development stages, and the correlation between sugar contents and sucrosemetabolizing enzymes activities were analyzed for exploring the difference of sugar accumulation on the physiology and illustrate the mechanisms of quality formation and regulation in Lycium fruit. Results showed that: (1) eight kind of sugars were detected in ‘Ningqi No.1’ by using gas phase chromatography (GC), seven kind of sugars were detected in ‘Ningxiahuangguo’ and four were detected in ‘Heiguo’. The main sugars were fructose , glucose and sucrose at mature stage. (2) The contents of fructose and glucose increased gradually with the fruit growth and development, and the growth rates of sugar contents in fruit developing late stage was significantly higher than that in the early stage. The sucrose and erythrose contents showed various changes during fruit development stages, and there were greatly different among Lycium at different developmental stages. (3) The activities of three sucrosemetabolizing enzymes have great difference in three different color fruits of Lycium during fruit development process. The acid invertase (AI) activity was low at fruit developing early stage and had no significant differences among materials, but it was high at late stage and had significant difference among materials. The activities of AI and sucrose phosphate synthase (SS) in three materials were higher than those of neutral invertase (NI) and sucrose phosphate synthase (SPS) from coloring fruit phase to fruit maturity phase. The content of fructose and three sucrosemetabolizing enzymes activities in‘Heiguo’ maintained a lower level during fruit development process. (4) Fructose content and AI activity were significantly (P＜0.05) and positively correlated among three different color fruits of Lycium. The hexose (fructose and glucose ) content and NI activity were significantly (P＜0.05) and positively correlated among red and black fruits. This suggests that sugar constituents and sucrosemetabolizing enzymes activities had large differences among three Lycium, increasing AI activity was favorable to fructose accumulation and invertase played an important role in hexose accumulation in Lycium fruits.