Aim Protective immunity of DNA vaccine pCDSj32 for Schistosoma japonica by different injection times and challenge time after the last inoculation in mice was investigated. Methods 100μg/100μl DNA vaccine pCDSj32 was injected into the quadriceps muscles of the BALB/c mice. The mice were divided into once immunized groups and three times immunized groups. Challenge infection was applied 4wk or 8wk after the last inoculation with 40 cercariae each mouse. The adult reduction rates and the EPG in the livers of mice were detected 6wk after challenge. Results Substantially protective immunity was obtained when compared the immunized groups with the control. The adult reduction rates were 35.61～44.44 ％ ,and the egg reduction rates in the livers were 39. 64～69.06％. Conclusion The protective immunity could be influenced by different times of DNA vaccine inoculation and the challenge time after the last immunization. The best protective results could be obtained with inoculation once combined with the challenge 8wk after the immunization of DNA vaccine.