Effects of replacement of trash fish with formulated diets on growth performance,body composition and fatty acid composition of Chinese mitten crab(Eriocheir sinensis)were investigated in this study.The culture tests were carried out at Chongming County,Shanghai,which lasted 240 days,from March to November.The survival and weight gain of each treatment were counted after breeding.Random sampling and then the hepatopancreas index(HSI),gonad index(GSI),meat percentage,body composition and fatty acid composition of each tissue of both male and female crab were determined.The result indicated that the formulated diets treatment had no significant influence on trash fish treatment in survival,weight gain,HSI,GSI and meat percentage(P>0.05).The moisture content in hepatopancreas of female and male crab of trash fish treatment were significantly higher than the formulated diets treatment(P<0.01),and the moisture content in meat of male crab of trash fish treatment was significantly higher than that of formulated diets treatment(P<0.01).Total lipid in hepatopancreas and gonad of female and male crab of trash fish group were significantly lower than that of formulated diets(P<0.05),and total lipid in meat of female crab of trash fish was significantly lower than that of formulated diets(P<0.05).Crude protein in hepatopancreas of female and male crab of trash fish was significantly higher than that of formulated diets(P<0.05),while crude protein in ovary of female crab of trash fish was significantly lower than that of formulated diets(P<0.05).Free fatty acid(FAA)in hepatopancreas of female of formulated diets treatment was significantly higher than trash fish treatment(P<0.05),and phospholipids(PL)content in hepatopancreas of female of trash fish treatment was significantly higher than formulated diets treatment(P<0.05).Triglycerides(TG)in both ovary and muscle of female of formulated diets treatment were significantly higher than trash fish treatment(P<0.05 or P<0.01),while FAA and PL contents of female of trash fish treatment were significantly higher than formulated diets treatment in ovary and muscle(P<0.05 or P<0.01).Cholesterol(CHO)in muscle of female of trash fish treatment was significantly higher than formulated diets treatment(P<0.01).There were no significantly differences in hepatopancreas of two treatments(P>0.05).FAA and TG in testis of trash fish treatment were significantly higher than formulated diets treatment(P<0.01),while PL in testis of trash fish treatment was significantly lower than formulated diets treatment(P<0.05).CHO in muscle of male of formulated diets treatment was significantly lower than trash fish treatment(P<0.01).Linolic acid(C18∶2n-6)in hepatopancreas and meat of male crab of trash fish were significantly lower than that of compound feed(P<0.01 orP<0.05),while ARA(C20∶4n-6)in meat of trash fish was significantly higher than that of compound feed(P<0.05).Linolenic acid(C18∶3n-3),DHA(C22∶6n-3)and ARA in ovary of female crab of trash fish were significantly lower than those of compound feed(P<0.01 orP<0.05).The results obtained from the present study indicated that suitable compound feed replacement of trash fish had no significant influence on growth and development of crab,while body composition and fatty acid composition of crab changed with different feeds