Abstract: To study the immune response, estrus and tissue distribution of inhibin after inhibin gene immunization, 60 rats were divided into five groups and immunized (i.m.) with 10（T1）,50（T2）,100 μg pCIS（T3）, 50 μg pcDNA3.1（V）and 0.85%NaCl (S) respectively. The antibody against inhibin was detected by ELISA, the estrus was detected by vagina smear and the tissue distribution of inhibin was detected by immunohistochemistry. The results showed that the P/N value of inhibin antibody went up significantly at day10 after 1st booster（P<0.05）and the P/N value in T2 and T3 group raised significantly at day 20 after 2nd booster（P<0.05）. The P/N value in T3 group was slightly higher than those in the T1 and T2 group（P>0.05）. The estrus was not affected. The immunohistochemistry results showed that there was no positive staining in the tissues such as heart, liver and muscles at inoculated sites, however, positive staining occurred in ovary, kidney and pituitary for both the experimental and control groups 2 weeks after 2nd booster. In the spleen, positive staining appeared in the experimental groups, but not in the control groups. These results suggested that the increased immunization time and dosage of inhibin DNA did not cause significant immunologic tolerance. The inhibin gene is safe to immunize rats and the tissue distribution of inhibin also provides important evidence to elucidate the mechanism of gene immunization.