Seven triploid seedless watermelon cultivars,including 6 red and 1 yellow flesh,were sampled to determine their fructose,glucose,sucrose and total sugar contents in different parts of the fruit.Fructose,glucose,sucrose and total sugar contents of 3 uncut red flesh seedless watermelon cultivars were assayed after 2 month storage at room temperature.The results showed that fructose,glucose,sucrose and total sugar contents were significantly different among cultivars and parts of seedless watermelon fruits.The fructose,glucose,sucrose and total sugar contents in heart portion were higher than portion near rind.The correlation between fructose,glucose,sucrose and total sugar contents in different parts was significantly(P 0.01).The losses of fructose,glucose,sucrose and total sugar contents were different among uncut seedless watermelons after 2 months storage at room temperature.The losses of fructose and total sugar contents in different parts of fruits were 20%-80%,the losses of glucose were 10%-60% and the losses of sucrose were 1%-25%.The ratio of fructose ∶ glucose ∶ sucrose of yellow-flesh and red-flesh watermelon fruit in ripen stage were about 6 ∶ 3 ∶ 1 and 5 ∶ 3 ∶ 1, respectively.