ObjectiveTo explore the etiologies of fever of unknown origin(FUO) and methods for confirming diagnosis in patients at a hospital, and provide reference for clinical diagnosis and treatment of FUO.MethodsPatients with FUO admitted to a hospital between January 2008 and July 2014 were performed clinical diagnosis with methods of serology, bacteriology, molecular biology, bone marrow aspiration, tissue biopsy, and diagnostic therapy, the etiologies and final diagnosis of 224 patients were analyzed retrospectively.ResultsOf 224 FUO cases, 189(84.38%) eventually got confirmed diagnosis, 35 (15.62%) were not confirmed. The percentage of infectious diseases, connective tissue diseases, malignant tumor, and other diseases were 50.45%,18.75%, 9.82%, and 5.36% respectively. Among infectious diseases, the major pathogens were bacteria, followed by virus. The major connective tissue diseases were systemic lupus erythematosus and  polyarteritis nodosa; the main malignant tumor was hematological tumor, lymphoma was the main form. Among 189 patients with confirmed diagnosis, 30.16% and 24.34% were performed pathogenic and pathologic detection respectively, and 20.11% were performed the other (comprehensive) methods.ConclusionInfectious diseases, connective tissue diseases, and tumor are major etiologies of FUO.