Abstract: Huangqin decoction is a classic formula for treating diarrhea in febrile diseases, and later became the basic formula for treating damp-heat diarrhea in the successive generations. This study introduces the expanded applications and the characteristics of its applicable population. In addition to the original text of Treatise on Cold Damage, Huangqin decoction can also be used in modern clinical practice for febrile diseases, gastrointestinal diseases, obstetrical and gynecological diseases, as well as autoimmune diseases. From the viewpoint of the applicable population, Huangqin decoction is mostly applied for a yin-deficiency or damp-heat constitution caused by internal heat or latent heat, which is more common in female population. Besides, it has specificity to apply the formula based on some typical symptoms or syndromes, such as mucosal hyperemia, dysphoria with smothery sensation, and anorectal discomfort. Thus, the mentioned syndromes are also called the indications of Huangqin decoction. The clinical thinking of identifying the indications of Huangqin decoction is inseparable from its applicable disease and applicable population.