Twenty four dairy cows at 7 d after calving were randomly assigned to four groups (three immunized group and one control group), the three immunized group of cows were primarily immunized (injection day as 0 d) with 3 mL (per cattle cow) of recombinant bacterium C500(pXAIS) delivering the inhibin gene vaccine (a kind of DNA vaccine Twenty four dairy cows at 7 d after calving were randomly assigned to four groups (three immunized group and one control group), the three immunized group of cows were primarily immunized (injection day as 0 d) with 3 mL (per cattle cow) of recombinant bacterium C500(pXAIS) delivering the inhibin gene vaccine (a kind of DNA vaccine without antibiotic resistance gene) in a high (1010 CFU/mL), middle (109 CFU/mL) or low (108 CFU/mL) dosage, the control group of cows were intramuscularly immunized with physiological saline (3 mL per cattle cow). The booster immunization (the same dosage as the primary immunization) was performed 28 d after primary immunization. The B ultrasonography was used to investigate the effect of inhibin gene vaccine on antibody level, involution of uterine cervix and uterine gravid horn of the postpartum dairy cows. The result showed that the booster immunization could raise antibody level against inhibin, which in T1 and T2 group was higher than that in CK (P<0.05). Furthermore, positive antibody percentage 7 d after booster immunization in T3 group was the highest, which was 83.33%. Diameters of both postpartum uterine cervix and postpartum gravid uterine horn in all groups decreased sharply during the first 21 d and then decreased gradually during the final 7 d within 30 d after inhibin gene vaccine immunization. Days of the uterine cervix involution were shorter (P>0.05) in the three immunized groups than those in control group, the same as those of the gravid uterine horn involution except for the remarkable difference (P<0.05) between T1 group ((28.75±1.92) d) and the CK group ((33.75±1.09) d). These findings demonstrate that inhibin gene vaccine C500(pXAIS) can enhance the immune response, stimulate restoration of uterus of the postpartum dairy cows.