Abstract: The biochemical substances in protoscolex of Echinococcus granulosus were investigated systematically by histochemical techniques.It was showed that glycogen,RNA,DNA,protein bound α-amino groups,tyrosine,tryptophan,histidine,alkaline protein,acid mucopolysaccharides,collagenous fibers,reticular fibers,activities of AKP,ACP and ATPase were detected at various levels in protoscoleces of Echinococcus granulosus.The content of glycogen was rich in parenchymal tissue of larva.RNA and DNA were mainly located in cytoplasm and cell nucleus,respectively.The content of protein bound α-amino groups,tyrosine,tryptophan,histidine and alkaline protein were very rich in tegument and small parenchymal cells.Both the activities of AKP and ATPase were very strong in tegument of protoscoleces.The hooks were contained heavy acid mucopolysaccharides and reticular fiber element and moderate contents of protein bound tyrosine,tryptophan and histidine.The collagenous fibers were noly presented in parenchymal tissue of larva.Some content of PAS positive material,RNA,DNA,protein bound α-amino groups,tyrosine,tryptophan and histidine,alkaline protein,acid mucopolysaccharides,collagenous and reticular fiber elcment,AKP,ACP and ATPase were found in calcareous corpuscles of protoscoleces.The physiological significance of biochemical substances presented in protoscoleces obtaincd from sheep was discussed briefly.