The author holds the point of view that lesser yang diseases do not locate in half interior and half exterior. Form the aspects of diverse indications of Xiaochaihu decoction, it is believed that Xiaochaihu decoction is not the main formula for the treatment of lesser yang diseases, and it is not only used to treat lesser yang diseases. It can be concluded that the core idea of applying classical prescriptions shall be integration of decoctions and syndromes. Seizing core pathogenesis is the right and flexible application of Zhongjing’s classical prescriptions.