The dosage， dose and administration method of decoctions are important factors affecting the efficacy of prescriptions. By analyzing 35 decoction formulas from the Ming and Qing dynasties within the Catalogue of Ancient Classic Famous Formulas （First Batch）， it was found that the average dosage was equivalent to about 65 g， of which 71.4% （25/35） of the prescriptions had a dosage ≤60 g. And among them， the dosage of decoctions in the Ming dynasty was significantly smaller than that in the Qing dynasty. Considering the characteristics of formulas in Song dynasty， it is believed that decoctions in Ming and Qing dynasties were influenced by the popular use of decoctions during the Song， Jin， and Yuan dynasties. Some decoctions recorded a dosage of one dose instead of one day， which was more evident in the Ming dynasty. However， by the Qing dynasty， the usage of prescriptions with a dosage of one day gradually became more common. Therefore， in the practical research and application of classic famous formulas from the Ming and Qing dynasties， it is advised to pay attention to the difference between the dosage， one dose and the daily dosage. It is necessary to determine whether to double the dosage of the original formula based on the actual use， in order to ensure the clinical efficacy.

Due to the difference between the system of weights and measures， and the dosage of clinical prescriptions of traditional Chinese medicine in various historical periods， the dosage and conversion standard of prescriptions in past dynasties are different. Therefore， when discounting the dosage of famous classical formulas， the principles of inheriting the essence， making the past serve the present， linking the past and the present， and forming a consensus should be followed， firstly， the dosage of the prescription was converted according to the weights and measures system of the past dynasties. If the converted dosage significantly exceeds the provisions of the 2020 edition of Chinese Pharmacopoeia， then on the premise of ensuring that the proportion of the original prescription drug dosage remains unchanged， the conversion shall be based on expert consensus and drug safety evaluation. For drugs measured in non-standard units， a conversion range is provided based on comprehensive literature analysis and physical measurements. For the conversion of service volume， the original text was used as the basis for the conversion with reference to the measurement standards of different eras. If the original dosage is not clear， the converted dosage will be determined based on the historical evolution of the formula， referring to relevant ancient books， and combining modern applications. Eventually， the converting standard for famous classical formulas was determined as follows：during the Han and Tang dynasties， one Liang（两） was equivalent to 13.8 g and one Sheng（升） was equivalent to 200 mL， in the Tang dynasty， one Fen（分） was equivalent to 3.45 g， during the Song， Jin and Yuan dynasties， one Qian（钱） was equivalent to 4.13 g and one Zhan（盏） was equivalent to 300 mL， during the Ming and Qing dynasties， one Qian（钱） was equivalent to 3.73 g， and one Bei（杯） and one Zhong（盅） were equivalent to 200 mL. For drugs recorded in non-standard units of measurement， it is necessary to conduct actual measurements to determine their conversion standards based on comprehensive analysis to determine their origin. If necessary， different records of the dosage of drugs with the same or similar efficacy and indications in medical books of similar ages can be used to assist in determining the conversion standards. The analysis of the principle of dosage conversion for Chinese medicine is helpful for the clinical application and development of famous classical formulas.