Double-layer bagged and unbagged pear fruits of Pyrus pyrifolia Nakai cv.‘Cuiguan’ were used in this study,to explore the variation patterns of sucrose,fructose,glucose,sorbitol and related enzyme activities.The results showed that,compared to unbagged fruit,the bagged fruits had lower fructose,glucose,sorbitol and sucrose.In comparison with unbagged fruits,the sorbitol dehydrogenase activity of bagged fruits was lower during the former 5 days storage,but higher after 10 days storage.The activity of sucrose phosphate synthase (SPS) and sucrose synthase (SS) in the fruits had the same tendency,was high for early period and low for late period during storage.The correlation analysis of the 4 kind sugars in the fruit during storage was made,we got that sorbitol and fructose had a significant negative correlation.Also,sucrose and glucose showed significant negative correlation.We concluded that sorbitol transformed to fructose,and sucrose transformed to glucose during storage.