In this article, the author attempts to reveal the actual meaning of “white soup” and shows its importance to the pharmacology of traditional Chinese medical formulas by summarizing the custom of decocting tea soup and taking tea as medicine in the Song dynasty and using Four gentleman decoction as an example. “White soup” recorded in Prescriptions has certain regularity in the application. On the basis of a brief literature review on medical practices and the habit of drinking tea in Song dynasty, the author believes that “white soup” in the Prescriptions refers to brewed regiment tea. Although the Four gentleman decoction has no herb that can “activate qi”, it has gained the effect of“activate qi”through the use of “White Soup”. Chinese medicine practitioners came after may get inspired from it and hence created many formulas that can “fill up your body with Qi” without causing “Qi congestion”.