Abstract: In order to study the influence laws of chitosan on fruit growing in papaya, different concentrations of 0, 0.1, 0.5 and 1.5 mg/mL were sprayed onto leaves during flowering period, based on variety of‘Sun-Rise mid-white skin’papaya, total dry weight and contents of important materials including soluble solid, soluble sugar, protein, organic acid and ratio of sugar and acid in papaya fruit during fruiting period were studied. The results indicated:①the dry weight of per fruit under chitosan treatment increased more quickly and longer than control group during fruiting period, so the dry weight at last was higher significantly, increasing by 20.44%.②During the whole fruiting period the contents of soluble solid, soluble sugar, protein and organic acid of papaya fruit under chitosan treatment were higher than control group except protein from 90th to 110th. Their speed during quick-growing was much higher than control.③The ratio of sugar and acid under chitosan treatment was lower during 10th to 50th but higher during 50th to 117th than control. In short, the chitosan treatment was helpful on increasing the dry weight and contents of important materials of papaya fruit, was helpful on improving the taste of papaya fruit, the optimal concentration was 0.5 mg/mL.