Abstract: The localization of some enzyme in adult worms of Clonorchis sinensis was studied by histochemical method in this paper. Acid phosphatase was detectcd mainly in digestive duct, subtegument and tne walls of testis, uterus and ovary; acetylcholinestcrase was found in oral sucker, ventral sucker, pharynx; and ATPase was found to exist in oral sucker, ventral sucker, pharynx and musclxe layer in the subtegument. The eggs of C. sinensis possessed the above three enzymes (Figs.l-5).