Abstract: Biochemical composition of male reproductive system and hepatopancreas, w ith special reference to lactate dehydrogenase( LDH) activity, was determined in the Chinese mitten-handed crab, Eriocheir sinensis . The results reveal that the glandula accessoria and luminal contents( seminal plasma along with spermatophores) are rich in carbohydrates ( 33. 456mg .. g - 1 and 21. 537mg .. g - 1 of wet t issue weight, respectively ) . The carbohydrate contents of hepatopancreas and spermatophore and testis are low . Luminal contents and hepatopancreas contain the highest level of gluco se and glycogen respectively, but spermatophore contains very low level of gluco se and in testis and hepatopancreas glycogen is too low to be detected. Protein content of hepatopancreas is higher than that of other tissues. Hepatopancreas and testis contain the higher level of lipid. Triglyceride exists in the hepatopancreas and testis only and the content of hepatopancreas is higher than that of testis. LDH activity is very high in seminal vesicle, and probably this is due to the storage of seminal substances within this region. On the contrary, spermatophores show only moderate amount and a low LDH activity detected in the seminal plasma may be due to it s leakage f rom the spermatophores. Compared with reproductive system, LDH activity of hepatopancreas is significantly low. All results show that the pattern of sperm metabolism in Eriocheir sinensis is anaerobic by utilizing carbohydrates. A high carbohydrate content of glandula accessoria suggests that spermatozoa may rely on carbohydrate reserves of seminal vesicle for its survival in the spermatheca.