Abstract: 【Objective】 This project aims to explore the sugar accumulation patterns and enzyme activities in sugar metabolism during fruit development.【Method】15 years old Korla fragrant pear (Pyrus brestschneideri Rehd) trees were used as material to analyze the variation of the major soluble sugar contents and related enzyme activities in sugar metabolism.【Result】Results showed that at early stage, sorbitol was the main component of soluble sugars accounting for more than 50% of total soluble sugars, and the proportion of sobitol tended to decrease along with the development of young fruits. However, the proportion of fructose, glucose and sucrose rose slowly at the later stage, and the fructose content surpassed the sorbitol to become the main sugar in the fruit. In the ripening stage, total soluble sugar contents increased to 16.16%, and fructose, sorbitol, glucose and sucrose contents accounted for 38.7%, 24.7%, 22.0% and 14.4% of total sugar content, respectively. The activities of acid invertase (AI) and neutral invertase (NI) were relatively low at early stage and increased strongly with fruit development. The sucrose synthase activity (SS) reduced at the early stage, and increased gradually at the later period. SPS activity increased slowly during the early stage of fruit growth,but showed a steep rise afterwards when sucrose accumulated sharply at the ripening stage. Variation trends of sorbitol dehydrogenase (SDH) and sorbitol oxidase (SOX) activities were basically the same, decreased at the early stage and then increased at the later stage. 【Conclusion】In the process of fruit development, the accumulation of total soluble sugar is mainly influenced by sorbitol, sucrose, glucose and fructose have little contribution to the total soluble sugar. Sorbitol is the main component of soluble sugars at early stage, However, at the ripening stage, fructose content surpassed the sorbitol to become the main sugar in the fruit.