Objective To evaluate the effect of transdermal agent of PZQ on infection of Schistosoma japonicum in different developmental stages and the early period of re?infection. Methods All Kunming mice in the experiment groups were infected with 40 ± 2 Schistosoma japonicum cercariae. The mice which were infected once and re?infected were treated by abdominal trans? dermal agent of praziquantel. Control groups were set for all of the experiment groups. All of the mice were dissected 42 d after the infection, and the worm reduction rate, egg reduction rate and miracidium hatching reduction rate were calculated. In addition, the dynamic changes of IgG antibody in sera of the mice were detected by ELISA in different time of primary infection and re?infection. Results The worm reduction rates of 1, 7, 14, 21 and 28 d after the infection were 48.9%, 0%, 28.8%, 84.3% and 70.2%, respec? tively, and those of 1 d and 14 d after re?infection were 85.6% and 90.8%, respectively. After the primary infection, the specific IgG level gradually increased with the prolongation of time, and the ratio of P/N of specific anti?ESA of IgG was significantly raised after re?infection. Conclusion The transdermal agent of praziquantel is effective to Schistosoma japonicum at developmental stag? es, and the effect to schistosomula at early period of re?infection is more significant.