Abstract: The effects of water-borne Cu2+on the molting rate, the weight gain and the survival rate of iv stage juvenile(0.020 ?0.01 g) and 12-month-old(3.34 ?0.26 g) Eriocheir sinensis were studied1The 24-, 48-,72-and 96-h LC50s of Cu2+on juvenile E.sinensis were 0.70, 0.43, 0.33 and 0.22mg/ L, respectively1Those on the 12-month-old E1sinensis were 18.20,10.23, 9.12 and 8.51mg/L, respectively.All the LC50s obtained in 12-month-old E.sinensis were higher than those in the juvenile ani-mals1The LC50s decreased in accordance with the increase of copper exposure time in both stages of E.sinensis.Effects of differ-ent levels of water-borne Cu2+(0.00,0.01, 0.02, 0.03.0.05, 0.80mg/L) on the molting rate,weight gain and survival rate of iv stage juvenile were determined1The results showed that after 11 days of Cu exposure, the survival rate for the juveniles were all above 50%, and it decreased in accordancewith the increase of Cu2+level1The highest survival rate(92.50%) was found in the control group, while the lowest(57.50%) was found in the 0.08mg/L Cu2+treated group.There was no significant difference in the survival rate between the control group and 0.01, 0.02 mg/ L Cu2+treated groups1In contrast,those treated with 0.03mg/L Cu2+or higher concentration were significantly different with the controls1The weight gain decreased in accordance with the in-crease of water-borne Cu2+level.The highest weight gain (228.43%) found in the control group, while the lowest gain (68.50%) was detected in 0.08mg/ L Cu2+treated group1There was a significant difference between the 0.08 mg/L copper treated group and the control group(P2+treated group1It should be noted that even in the 0.01 mg/ L treated group copper had a significant inhibition(P2+levels1Except in 0.01mg/L Cu2+treated group, there was a significant difference of the survival rate in all Cu2+treated group with the controls(P2+levels; however, it generally decreased in accor-dancewith the increase of water-borne copper concentrations.The highest weight gain(177.00%)was in control group,while the lowest weight gain(16.38%) was in 2.5 mg/ L Cu2+treated group.Similar variation tendencies were observed on molting rate1It decreased in accordancewith the increase of copper level,with the highest molting rate(165.00%) in control group and the low-est value(45%) in 1.00 mg/ L and 2.50 mg/ L copper treated group1There was a significant difference(P2+or higher treated groups1The correlation coefficients between water-borne copper concentra-tion and the survival weight gain, and molting rate in juvenile E1sinensis was-0.953,-0.852 and-0.911, respectively; and those in 12-month-old E1sinensis was-0.842,-0.646 and-0.802, respectively, suggesting a significantly negative correla-tion(Pearson correlation test P< 0.01) between the water-born copper concentration and these rates of E.sinensis.