Abstract： Starting from the pathogenesis of Xiaochaihu tang syndrome(weak yang- qi lacking the strength to defend pathogens)，through the further discussion on the theory of half-exterior and half-interior of CHENG WUji，this paper puts forward that the characteristics of heat-type alternating chills and fever should be “the intermittent occurrence of aversion to cold with fever，or，fever only”. And it is believed that the intermittent occurrence of aversion to cold with fever is only a special case，which is not easy to differentiate in clinical practice and does not show general guidance.