The external application of Chinese medicine is to use the principle of Chinese medicine to return to the meridian, leading the group of drugs with thick smell as the guide, opening the knot and moving the stagnation to reach the foci of the disease, which can penetrate into the skin and produce the effect of activating blood stasis, opening the meridian, penetrating the bone, dispelling wind and dispersing cold. The Chinese medicine applied to the body surface stimulates nerve endings, dilates blood vessels through reflex, promotes local blood circulation, improves nutrition of surrounding tissues, and achieves the purpose of reducing swelling, anti-inflammation and analgesia. At the same time, the drug penetrates through the skin at the affected area to reach the subcutaneous tissues, producing a relative advantage of drug concentration in the local area, thus exerting a strong pharmacological effect.