Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species in China,and its market price is largely depengding on their size.The large size E.sinensis generally has the 2-5 times of price than the smaller,but it remain unknow whether their nutritional quality is affected by the market size.This work aims to investigate the size effect on gonadosomatic index (GSI), edible yield and nutritional composition of adult male E. sinensis and four grades of crabs, i.e Grade Ⅰ: 200-249 g; Grade Ⅱ: 175-199 g; Grade Ⅲ: 150-174 g; Grade Ⅳ: ≤ 150 g, was used in this sutdy.