The purpose of this study is to determine whether two-step method of diagnostic strategy is effective in the diagnosis and treatment of fever of unknown origin (FUO). (TSMD research, a pilot study) Fever of unknown origin (FUO) is a fever in excess of 38.3◦C continued for more than 3 weeks, and its cause could not be identified by tests during hospitalization for more than 1 week [1]. As diagnostic techniques such as imaging technology and clinical tests have been developed and outpatient access to diagnostic tests have improved, the FUO is defined as a shortened period where the cause could not be revealed despite diagnostic tests during three visits to the outpatient department or during 3 days of hospitalization [2]. FUO can be caused by many diseases, and causes can vary depending on region and time period. FUO was first reported in the medical literature 80 years ago. Since then, the causative diseases have greatly changed with changes in the social environment and widespread use of diagnostic imaging. The causes of FUO, according to traditional diagnosis and treatment, could be divided into four principal groups: infections, non-infectious inflammatory diseases (NIID, including rheumatic diseases and vasculitic diseases), neoplasms, and other diseases. Despite the development of various diagnostic techniques, 34-51% of FUO patients remain undiagnosed [3,4]. In China, over-reliance on antibiotics for disease therapy and infection prevention are common phenomena in traditional treatment of FUO[5].