Abstract: Two individuals（GT-Y10，DT-Y168），showing comparative higher or lower sugar content with fruit respectively，from the population of‘Yali’בJingbaili’were taken as materials. The contents of total sugar，sucrose，fructose，glucose，sorbitol and the activities of sugar related metabolizing enzymes were analyzed and compared. Results showed that the content of fructose in GT-Y10 and DT-Y168 was the highest，and accounted for 45.77% and 50.98% of total sugar content；The content of sorbitol following as the second，and the content of sucrose was comparative lower. At the stage of fruit ripening，the content of fructose in GT-Y10 was lower than that of DT-Y168，while the content of sucrose，glucose，sorbitol were higher in contrary，and resulted in total sugar difference between GT-Y10 and DT-Y168. The key enzyme that resulted in the difference of sucrose content between GT-Y10 and DT-Y168 was the sucrose synthase （synthetic activity），the difference of glucose and fructose content between GT-Y10 and DT-Y168 were mainly resulted by NAD⁺-dependent sorbitol dehydrogenase and NADP⁺-dependent sorbitol dehydro- genase，meanwhile it also affected by acid invertase，neutral invertase and sucrose synthase（cleavage activity）. The activity of NAD⁺-dependent sorbitol dehydrogenase and NADP⁺-dependent sorbitol dehydro- genase also made contribution to the difference of sorbitol content between GT-Y10 and DT-Y168.

Key words: pear, hybrid individual, sugar, related metabolizing enzyme