Abstract: The Chinese mitten-handed crab Eriocheir sinensis, is considered to be a good crustacean species for culture in China. There have been a lot of researches on its breeding, culture, treatment of disease and nutrition last years. But the physio-ecological study has not been reported, especially oxygen consumption data are lacking for Eriocheir sinensis. In this study, the effect of temperature and body weight on the metabolism of the juvenile Eriocheir sinensis (weighing from 0.40g to 5.19g) was conducted during Sept. to Dec., 1998 by normal aquatic chemical methods. A cone flask with 250mL of internal volumes was used as respiratory chamber and was filled with tap water that was dechlorined for 7 days. Dissolved oxygen (DO) levels were determined using the Winkler method and free CO2 quantity was determined by a phenolphthanlein indicator with the NaOH standard solution used. The Nessler reagent method was used for determination of the NH3-N quantity. The fasting metabolic rate of the crabs of three weight groups (3.64, 1.69 and 0.52g) was determined at the temperature of 15, 20, 25 and 30℃ also. The experimental results showed both oxygen consumption (RO, mg/g/h) and excretion rate of ammonia-N (RN, g/g/h) were affected significantly by water temperature (T, ℃) and body weight (W, g). RO and RN increased with increasing temperature and decreased with increasing body weight. The relationships could be expressed as: R O=0.1309e0.0490T (r=0.8391, n=75, p0.01) and RN= 3.3649e0.0484T(r=0.6999, n=75, p0.01); R O=0.4254W-0.1999 (r=-0.5094, n=75, p0.01) and RN= 0.4400W-2.900 (r=-0.6237, n=75, p0.01), respectively. The compound correlation between temperature, weight and ROO-0.2138e 0.0504T (r=0.9876, n=75, P0.01); and the same relationship for RNN-0.3032e0.0502T (r=0.9563, n=75, p0.01). The ratio of oxygen to nitrogen was not significantly affected by temperature (p0.05) but markedly influenced by crab's body weight (p0.01). The fasting metabolic rate also decreased with increasing body weight and increased with increasing temperature. The ratio of metabolic substrate-protein, lipid and carbohydrate at three groups of juvenile crab weighing 3.64, 1.69 and 0.52g were 6.4:41.8:51.8, 6.7:27.8:65.5 and 7.3:43.8:48.9, respectively. The ratio of protein gradually increased with decreasing body weight. But the ratio of metabolic substrate was not regularly affected by temperature.