The effects of Hou po（Cortex Magnoliae Officinalis） used in the prescriptions of Zhang zhongjing were regulation Qi and descent adverse flow of Qi ， elimination stagnation， regulation the vital energy and dissolution the mass. Through the compatibility of different drugs， Houpo plays the different functions with the different doses to cure the disease in tri-jiao. The characteristics of Houpo applied by zhongjing provided a reference for us in cure disease.