Fever of unknown origin (FUO) is a disease whose causes remain unknown according to the pathients′ clinical information. Nowadays, FUO becomes a hard nut to crack. For modern medicine, the pathogenesis of FUO has not been found, and the results of clinical examinations are negative, so the therapies of FUO are often symptomatic treatment. However, in traditional Chinese medicine, we can apply kinds of therapies to treat FUO by syndrome differentiation and comprehensive analysis of data gained by four diagnostic methods. For FUO, we can not only use defervescent drugs in traditional Chinese medicine, but use different treatments according to cold, heat, deficiency or excess. Reconciling shaoyang is an effective therapy for FUO when exterior syndromes don′t relieve and the interior syndromes invade the organism.