Abstract: The contents of total sugar, sucrose, ducrose, fructose and the activities of sucrose-metabolizing enzymes containing acid invertase, sucrose synthase, sucrose phosphate synthase and amylase in the fruit flesh of Juglans regia L．were analyzed． The results showed that the highest content of total sugar was found in the late developmental stage, with the starch content being varied during fruit development an d contents of soluble sugars changing according to the kinds of sugars. The fructose content gradually decreased in the late developmental stage, but the contents of sucrose and the ducose increased．The activities of acid invertase and am ylase were higher at the early developmental stage than at the late developmental stage; and the activities of sucrose synthase and sucrose phosphate synthase showed a similar chan ge pattern with lower activities at the early developmental stage and higher activities at the late developmental stage．

Key words: Walnut, Flesh, Sugar, Acid invertase, Sucrose synthase, Sucrose phosphate synthase