Abstract: Objective To explore the risk factors associated with fatality among severe cases of pandemic influenza H1N1 in Nanchang city.Methods A case-control study was conducted with 9 cases of death and 66 severe cases of influenza H1N1 as controls.Results The ratio of the severe cases was 8.33% among all influenza A H1N1 patients.The mortality was 1%.The fatality of the cases with chronic liver disease,pregnancy,and invasive oxygen treatment was higher than that of severe cases with the odds ratio(OR)(95% confidence intervalCI)of 25.6(1.97-333.55),12.67(0.86186.91),and 10(1.07-93.44).Compared with the cases without complication,the fatality of the cases with 2 or 3 complications was higher with the OR(95% CI)of 9.83(1.17-82.94)and 118(8.72-1597).Conclusion The basic diseases (chronic liver disease,cardiovascular disease,pregnancy),with invasive oxygen treatment and complications are risk factors of fatallty for serere influenza A H1N1 patients.The case with the risk factors should be diagnosed earlier,monitored closely,and treated properly to reduce the fatality.