Objective To delineate the m orp hology and ecology of a new human schistosome species. Methods (1)Adult schistosomes were obtained from infected mice and rabbi ts with cercariae shedding from snails which were infected with miracidia devel oping from the eggs in feces of acute schistosomiasis patients. (2)T he rabbits were dissected during 60-100 d infection period of cecariae, and thei r bladders were taken out for detecting eggs in the urine. (3)Schistosome eggs i n the feces of patients were examined with microscopy. Results (1)There were two types of male worms: one was with an average o f size 8.76 mm long and 0 43 mm wide while the other with an average size of 2 41 mm long and 0 091 mm wide and with undeveloped gynecophoral canal which ap peared in front of ventral sucker (2)There were two types of female worms: one was with an average of size 10 73 mm long and 0 74 mm wide while the other wi th an average of size 3 43 mm long and 0 12 mm wide and was fine, semitranspar ent and tape like with undeveloped ovary and vitellaria. Less than 10 eggs or none were found in t he uterus. (3)There were a lot of degenerated and black eggs in the feces of 2 p atients. (4) Schistosome eggs were detected in the urine and miracidia were hatc hed out from 8 out of 16 infected rabbits.(5) Others: 8 worms were detected in 1 mouse out of 12 dissected mice for evaluation of infectious water with sentry m ice in spite of that no Oncomelania snails were found in the area. Cercariae stayed on water surface in lying position like a c omma. The eggs returned forwardly a fter growing behind the ovary in female worm. ConclusionAccording to the primary investigation in morphology an d ecology, the new schistosome obtained is distinct from the 6 well defined ty p es of human schistosome. It is considered that a new schistosome species should be foun d and temporarily nominated as Schistosoma nanjingi( S.n.)