Abstract: An experimental study of nithiocyamine in various dosage forms and courses of treatment was made on mice, rabbits, dogs and rhesus monkeys infected with Schistosomiasis japonica. The results showed a worm decrease rate of 90～100%. After treatment of the animals with this drug, the worms moved to the liver where the dead ones formed nodules. 6 months after treatment, no revival of the worms could be found. The therapeutic efficacy was good and stable and was directly related to the particle size of the drug.The actions of nithiocyamine on Schistosoma japonicum was observed through pathological, histochemical, indirect immunofluorescence and in vitro culture technique. It has been found that the drug has strong killing effects upon the worms, the minimum lethal concentration beingμg/ml. The drug forced the worms to move to the liver, then destroyed its surface membrane, disturbed the metabolism. It decreased the glycogen content and the activities of succinate dehydrogenase and ATPase. The experiments showed that the schistosomicidal action of nitiocyamine may involve several factors, of which the main one may be the damage or disturbance of the protective function and metabolism, especially glucose metabolism.