Jiulongzhai Sour Plum Soup, as a traditional drink in Beijing, can be traced back to the Qing Dynasty. It is said that a small vendor came to Beijing to take refuge in his uncle who works in the Imperial Tea Room. His uncle secretly sent him the secret recipe of palace drinks from the Royal Tea Room. Small traders make sweet-scented osmanthus sour plum soup for sale according to the secret recipe, which is sought after by Beijing people. Therefore, the stall owner asked fellow countryman Hanlin to name it "Jiulong Zhai". According to "Yanjing Years" published in Guangxu's thirty-second year, "Sour plum soup is boiled with sour plum and rock sugar, mixed with ice water of roses and osmanthus, which is cool and vibrates teeth. Jiumenzhai used to be the first in Kyoto. " Fang Junyi, a Taoist scholar, also wrote in his Miscellanies of Spring and Ming Dynasties: "The thirst-quenching plum soup has been chilled for a long time, and it has long been named Kowloon."

Despite its profound historical background, with the decline of the Qing court, various places fell into a melee among warlords, and the Jiulongzhai sour plum soup fell into a trough from then on. If it weren't for the intervention of Yanjing Group, the century-old brand of Jiulong Zhai might have slowly disappeared.