Objective To summarize the clinical dosage of Guizhi（Ramulus Cinnamomi

桂枝） since the Han Dynasties（2000 years ago） and provide a basis for formulating the clinical dosage strategy of Guizhi. Methods The database of clinical dosage of Guizhi through ages was established. The formulas containing Guizhi in the most representative medical books were selected and the formula name

total dosage

dosage of Guizhi

herb numbers in a formula

water consumption in decoction and method of administration were recorded. The frequency

the most common dosage

the upper limit of usual dose

the lower limit of usual dose

the maximum dosage

the minimum dosage and the average dosage of Guizhi were analyzed. The dosage characteristics of Guizhi through ages were analyzed.Results The dosage of Guizhi was large in the Han-Tang-Song Dynasties

with an average dosage of more than 20 g.The dosage of Guizhi was gradually reduced since the Jin-Yuan Dynasties. As a warm acrid herb

the average dosage and common dosage of Guizhi was decreased after the Ming and Qing Dynasties because of the prevalence of epidemic febrile disease theory. But some doctors still used large dose of Guizhi to treat some diseases with a maximum dosage of 298. 4 g. Conclusion The extra large dose of Guizhi is used to treat common cold with wind-cold exterior deficiency syndrome. The large dose of Guizhi is used to warm the channels and free the vessels.