Abstract: The binding capacity of the drug enrofloxacin with the plasma protein of Chinese mitten-handed crab, Eriocheir sinensis during feeding was investigated. The method of fixed equilibrium dialysis test was applied to the study on the binding of enrofloxacin with the crab blood plasma protein. Concentration of the plasma proteins in Chinese mitten-handed crab was 63.95±0.29 mg · mL^-1. Molecular weight of these proteins were mainly between 66.2~97.1 kDa. Protein binding level of enrofloxacin and crab plasma proteins was 47.39%~82.58%, showing that more than 50% of the drug could be bound to the proteins. Thus, it could be concluded that enrofloxacin can bind with plasma proteins tightly. So, in case of using enrofloxacin alone or with other medicine, its effective concentration and competition between drugs should be considered in Chinese mitten-handed crab culture.