Objective To investigate the clinical characteristics of patients with sever H1N1 influenza in Xinjiang region, and analyze risk factors related to patients’prognosis. Methods 63 patients with severe H1N1 influenza from September 2009 to December 2009, who came from five general hospitals and contagious disease hospitals were retrospectively studied. Data of baseline characteristics, treatment, and outcomes were collected. Results Among the 63 cases of severe H1N1 influenza patients, 46 patients survived, in which 30 cases were complicated with pneumonia( 63. 8% ) , 10 cases with MODS ( 43. 48% ) ;26 were male,20 were female; the median age was ( 28. 48 ±19. 59) years old.17 patients died, in which 11 were male, 6 were female; the median age was ( 39. 47 ±21. 23) years old. There were no significantdifferences in white blood cells, neutrophils, granulocytes, lymphocytes, Hb, platelets, CK-MB, HB, DH, UN,APTT, INR, K+ , Na+ , Cl - , PaO2 , SaO2 between the survival patients and the died patients ( P gt; 0. 05) .However there were significant differences in AST, ALT, CK, LDH, AL, CR, and pH ( P lt; 0. 05) .Conclusions Most of the patients with sever H1N1 influenza are young. The typical clinical manifestations are fever, cough, and expectoration. The patients usually are complicated with pneumonia. The patients complicated with MODS have a higher risk of death. Early administration of effective antiviral agents, low dose corticosteroids, and reasonable mechanical ventilation may improve the prognosis.