We evaluated the effect of salinity on the metabolism of female Chinese crabs (). The crabs, body weight (55.59 ± 6.24) g, were held at salinities of 0, 6, 12, 18 and 24, (16 ± 1) production, and ammonia-N excretion. Using this data, we calculated the respiratory quotient, oxygen-nitrogen ratio, energy consumption rate, and metabolic substrate ratio. Salinity had a significant effect on the oxygen consumption rate and ammonia–N excretion rate (<0.05). Between salinity 0–24, the rates of oxygen consumption and ammonia–N excretion both decreased as salinity increased. We observed a similar pattern for CO₂ production and energy consumption, but the differences were not significant relative to the control group at salinity 6 >0.05). Between salinity 12–24, CO₂ production and energy consumption were significantly lower than in the control group. Salinity had no effect on the respiratory quotient and oxygen–nitrogen ratio . Our results suggest that lipids are used preferentially as an energy source. Furthermore, proteins were utilized to a much greater extent than carbohydrates. The proportion of lipids in the metabolic substrate increased as salinity increased. Conversely, the carbohydrate metabolic substrate ratio decreased as salinity increasedwhereas the protein metabolic substrate ratio remained constant. At salinity 24, the ratio of protein, carbohydrate, and lipid used as metabolic substrate was 6.479.0. During the reproductive migration, the female Chinese crab migrates from fresh water into the Yangtze River estuary. Thus, individuals must adjust to the higher salinity and modify their energy metabolism. Our results suggest that energy consumption decreases after entering salt water, allowing female crabs to divert energy into reproduction.