The principles of addition and subtraction of Chinese herbal formulas include the addition and subtraction of flavors, and the addition and subtraction of dosages. 1. Addition or subtraction of medicinal flavor Formulas are composed of medicines, and when the flavor of medicines in a formula is increased or decreased, the function of the formula will be affected or changed. The addition or subtraction of medicinal flavor changes in order to make the selected formula more suitable for the changing needs of the condition, mainly in the case of clinically used formulas in the main disease, symptoms, etc. remain unchanged, change the secondary drugs to adapt to the changed condition. For example, Gui Zhi Tang, which is used to relieve the muscle (using sweating and other methods to make the evil qi trapped in the surface of the muscle go out) and regulate the camping and defense, is mainly used to treat the syndrome of external wind-cold and surface deficiency (a kind of syndrome manifested by fever, fear of cold, sweating, and fatigue, etc.), and when the patient develops coughing and wheezing on the basis of the syndrome, it can be added with Hou Pu and apricot to calm down the asthma, and this time, it is changed into Gui Zhi Plus Hou Pu and Apricot Soup. 2. Dosage The dosage of the drug directly determines the efficacy and strength of the drug, so even if the flavor of the drug in the formula remains unchanged, only the amount of the drug is changed, which will make the function and main treatment of the formula change. For example, Si-Reverse Tang and Tong Wei Si-Reverse Tang have the same composition of drugs, but Tong Wei Si-Reverse Tang has a large amount of dry ginger and epimedium, which has a stronger ability to restore yang and rescue reversal (through warming and tonifying yang qi to rescue fainting, unconsciousness, etc.) than Si-Reverse Tang, and it is used in the treatment of patients with critical illnesses. The above are the two aspects of the principle of formula addition and subtraction, if there is a need to add or subtract medicines, please operate by the physician after identification, do not blindly add or subtract medicines, so as to avoid the occurrence of medicines that are not suitable for the patient, aggravate the condition and other accidents.