Abstract: This paper deals with the alteration of tegumental surface of Schistosoma japonicum in the mice after oral administration of artemether suspension. Some of the female and male worms showed positive reaction in the indirect fluorescence antibody assay 1 and 5 days respectively after a single dose of 300mg/kg. Different degrees of intensity of fluorescent reaction were demonstrated in all mature female and about one-half of male worms on day 5 and day 9 respectively, and a part of bisexual worms still showed some positive reaction on day 12. The time of exposure of tegumental surface antigen, the number of worms so affected and the intensity of fluorescent reaction of worms were related to the dosage of drug administered. On day 5 after medication, none of the immature female worms showed positive reaction.