Abstract: The fine structure of the tegument of Schistosoma japonica was studied by means of transmission electron microscopy.Mice infected with schistosomes were treated with nithiocyamine (PEG Form) orally at the dosage of 24 mg/kg/day for three days. The worms that moved to the liver of the animals, 24 hours after this treatment, were studied by means of electron microscopy. The walls of worms including the tegument, muscle layers and tegumental cells were found to be affected. The decrease and disappearance of two major cytoplasmic inclusions in the tegument, multilaminate vesicles and discoic granules of the schietosomes seemed to be related to the pathological changes of its ultrastructure. The damages of the walls of the worms disturbed its' absorption, metabolism and protective function.Attempts have also been made to study the methods of ultrastructure section of Schistosoma japonica.