Disclosed are internal drug for treating chronic urticaria and a preparation method thereof. The internal drug is composed of, by mass, 1-3 parts of Chinese Atractylode rhizome, 1-3 parts of Poria cocos, 1-3 parts of white Atractylodes rhizome, 1-3 parts of Schizonepeta herb, 1-3 parts of peony bark, 1-3 parts of Chinese parsnip root, 1-3 parts of tribulus terrestris, 1-3 parts of muscardine cadaver, 1-3 parts of Szechuan lovage rhizome, 1-3 parts of red-rooted Salvia root, 1-3 parts of dragon's bone and 1-3 parts of Scutellaria root. The preparation method includes the following steps: selecting and purchasing Chinese Atractylode rhizome, Poria cocos, white Atractylodes rhizome, Schizonepeta herb, peony bark, Chinese parsnip root, tribulus terrestris, muscardine cadaver, Szechuan lovage rhizome, red-rooted Salvia root, dragon's bone and Scutellaria root which are high in quality, clean and first-class according to a mass part ratio, respectively removing impurities and dust, and sacking and tying for standby use; placing the components in cold boiled water for soaking for half an hour, placing the soaked components and supernatant liquid for soaking the components in a decocting machine, injecting cold boiled water higher than the components by 35mm for first-time decocting for 40 minutes, filtering to obtain drug liquid, injecting slightly warm boiled water higher than the components by 32mm for second-time decocting for 35 minutes, mixing and concentrating to form 1620ml of 50% traditional Chinese medicine liquid, bagging and sealing, and placing the traditional Chinese medicine liquid in a refrigerator for preservation and standby use.