Qingfei Paidu Decoction is a traditional Chinese medicine compound recommended by National Health Commission of the People's Republic of China and National Administration of Traditional Chinese Medicine for clinical therapies of coronavirus disease 2019(COVID-19). Qingfei Paidu Decoction consists of 21 traditional Chinese medicines, such as Asari Radix et Rhizoma. However, the dosage of Asari Radix et Rhizoma has been questioned by some people, because of one ancient proverb. To explore the rationality of the dosage of Asari Radix et Rhizoma in Qingfei Paidu Decoction, this study systematically examined the ancient and modern physicians' understanding of the toxicity of Asari Radix et Rhizoma, and collated the application and dosage of Asari Radix et Rhizoma in ancient prescriptions and modern clinics based on literature analysis. As a result, we found that ancient and modern physicians have different understanding on the toxicity of Asari Radix et Rhizoma and that the theory about the dosage of Asari Radix et Rhizoma is flawed. We also found that the dose of Asari Radix et Rhizoma in ancient and modern clinical applications was not constrained by ancient experience. Physicians usually increase the dosage of Asari Radix et Rhizoma in clinical therapy according to the actual conditions, and there were no adverse reactions. Additionally, according to laws and regulations concerning medical affairs, physician could increase or decrease the dosage of the drug under special circumstances. Based on the analysis of safety and effectiveness of Asari Radix et Rhizoma in Qingfei Paidu Decoction, we conclude that the dose of Asari Radix et Rhizoma in Qingfei Paidu Decoction is safe, effective and reasonable.