Although soap was not invented by China, and the modern soap industry is also imported, the word' soap' is an out-and-out domestic product, which originated from ancient China Gleditsia sinensis. This is a pod of Gleditsia sinensis in Leguminosae, which contains saponin and has the properties similar to surfactants: foaming, decontamination and emulsification. It is more resistant to hard water and alkali than real soap and harmless to silk and wool fabrics. There are many kinds of Gleditsia sinensis, and their detergency is different. It is recorded in the Newly Revised Materia Medica in the early Tang Dynasty that "Gleditsia sinensis is the lowest, with a thin evil shape and no moisture, which can't be washed away", so it is appropriate to choose "thin skin and meaty taste". Therefore, "Gleditsia sinensis" or "Gleditsia sinensis" is used to refer to high-quality and fleshy Gleditsia sinensis, which means "fleshy Gleditsia sinensis". The "soap ball" mentioned in the section "Little Broker" in Volume 6 of Old Wulin, which was carefully compiled at the end of the Southern Song Dynasty, refers to the pill ball made of coarse Gleditsia sinensis. Li Shizhen's Compendium of Materia Medica in the Ming Dynasty said: "Gleditsia sinensis ... picked in October, cooked and mashed, made into pills with white flour and incense, washed to remove dirt, but greasy and moist, better than Gleditsia sinensis". It can be seen that the soap saponified by modern chemical oil in China only follows the name of "Gleditsia sinensis", and the chemical composition has nothing to do with this kind of Gleditsia sinensis and soap balls. Although China did not invent exact soap products in ancient times, it indirectly used the chemical composition of soap.