Abstract: This paper reports the damage effect of immune serum and complement on mechanically transformed schistosomula of schistosoma japonicum. The schistosomula were incubated in the media which contained sera in different dilutions, complement, and serum with complement. Normal serum was used as control. The plates were then incubated at 37℃ in 5%CO2 incubator for 4, 16, 24, 48, 72, and 96 h. The activity of the schistosomula became low and some of the worms died after being incubated in fresh immune serum for 16 h. The mortality increased with the time of incubation. The mortality of the schistosomula was 58.3%, 58.5%, and 77.3% respectively after 96h in the media in which the ratio of medium to immune serum was 1:1, 1:2, and 1:9. In the medium with inactivated normal serum, the activity of the schistosomula was relatively normal and the dead worms were seldom seen. After the schistosomula were incubated for 4h in the medium which contained complement, the bubble-like substances appeared on the body surface of schistosomula. After 48 h, the body of worms wrinkled obviously. Some opaque particles appeared on the surface of the schistosomula. The mortality of the worms was 86.1% after 96 h. The mortality of the schistosomula in the medium in which B factor in serum had been eliminated was lower than that in the medium with fresh guinea pig serum. The highest mortality of the schistosomula occurred in the medium with immune serum and complement and was 98.13% when the schistosomula were incubated for 96h. The schistosomula in the medium with immune serum and complement were seriously damaged, as observed under scanning electron microscope. The spines on the body surface became inordinately arrayed or disappeared. Some part of the body surface was broken and stripped. The damage mechanism of the immune factors in the serum of the schistosomula is discussed.