Abstract: The immune effect of inactivated vaccine(Type II)prepaied with golden hamster cells 11510 individuals aged from 16 to 60 years old of 17 villages of Junan county with high incidence was reported.At 14 days one years after the three injections the seroconversion rates of neutralizing antibodies were 68.96%,18 52%.respectively.At 14 days one year,two years and three years after the fourth injections the seroconversion rates of neutralizing antibodies were 100%,60.00%.53.33%.50.00% respectively.The geometric mean titers were 8.4,3.2,17.05,5.75,5.39,3.69 respectively.The positive rates of fluorescent antibody were 92.00%,62.07%,100 00%,56.00%,32.00%,25.00%.In the four years after the basic immunization there were 1 and 61 cases in the immunized group and the control group respectively.The incidence rates were 2.17/100000 and 128.9/100000 respectively.The protective rate was 98.32% and the safety was good.After the epidemic peak the fluorescent antibody of six persons increased but they had no manifestation.Conclusion:The preventive effect of type II inactivated vaccine against HFRS was good and the immune enhancement cases were not found in four years after immunization.