Zheng qi is the ability of body resistance against disease. Xie qi are the pathogenic factors. Strengthening the zheng qi and dispelling xie qi are two differing therapeutic principles. Generally, strengthening the zheng qi is used where body resistance is weak and pathogenic factors are not strong; dispelling xie qi is applied to cases which have excessive pathogenic factors, and also an unweakened body resistance. First, strengthening zheng qi and then dispelling xie qi is used in cases where the zheng qi and xie qi are not weakened. The simultaneous strengthening of zheng qi and dispelling of xie qi is applied in cases of weak body resistance where pathogenic factors are in excess. When this principle is employed, one must differentiate between what is primary and what is secondary. In strengthening zheng qi, allow for unforeseen pathogenic factors, and when dispelling pathogenic factors, do not influence the body resistance. It is necessary to make the principles of strengthening body resistance and dispelling pathogenic factors complement each other.