Wu Ling San is mainly used for treating water-dampness or phlegm-drinking (pathological products formed as a result of water-liquid metabolism disorders) internal stagnation syndrome, and can be used in modern clinics for treating edema or gastrointestinal disorders caused by various etiological factors, and is not generally used in the treatment of popliteal cysts. Wu Ling San has the efficacy of inducing diuresis and seepage of dampness (promoting the flow of water to get rid of dampness), warming yang and transforming qi (warming yang qi in the body), and it can be used to treat water retention syndrome (a kind of syndrome manifesting as unsmooth urination, bloating of the abdomen, thirst for water and vomiting when finished drinking, etc.), which is characterized by unfavorable urination (unsmooth urination), headache with a slight fever, thirst and desire to drink, or even vomiting when water is consumed. This formula can also be used to treat phlegm-drinking, which is characterized by palpitations under the umbilicus, spitting saliva and dizziness, or shortness of breath and coughing; internal stagnation of water-dampness (water-dampness stays in the body), which is characterized by oedema, diarrhoea, dysuria, and vomiting and diarrhoea in cholera. The adverse reactions and contraindications of this formula are not clear. After discomfort occurs, one should consult a doctor in time and choose medication under the guidance of physician’s diagnosis, and should not use medication on one’s own in order to avoid delaying the condition.