Medically unexplained symptoms（ MUS） is a common medical phenomenon in general hospitals， which constitutes a serious financial burden on individuals and society. The pathologic mechanism of MUS is not yet clear， and there are obvious differences in the definition and diagnostic criteria. Since MUS is involved in both biological medical and psychiatry， it must be a multi-factorial problem. Finally， it is very important to establish the definition and operable diagnostic criteria for the clinical diagnosis and treatment of MUS.