By analyzing the unearthed bamboo and silk medical books between the Warring States Period and the Qin and Han Dynasties， namely

Formulas for Fifty

-

two Diseases

（《五十二病方》），

Disease Prescriptions and Others

(《病方及其它》） and

Wuwei Han Slips

（《武威汉代医简》）， it was found that the common liquid units for capacity in the prescriptions of the three medical books included standard units

sheng

（升），

dou

（斗），

can

（参）， and non-standard units

bei

（杯），

ou

（瓯），

weng

（罋） and

fu

（鍑）. This article proves that “

sheng

”， “

can

” and “

dou

”， the liquid units of prescriptions in the bamboo and silk medical books， had conversion relationship that 1

can

= 1/3 small

dou

， about 2.8~3

sheng

. And it is presumed that the liquid capacity unit 1

can

in bamboo and silk medical books between Warring States Period and Qin and Han Dynasties is about 560~600 ml in modern society. As a common utensil for eating and drinking， “

bei

” is often used as a unit for liquid capacity in prescriptions， and is proved that 1

bei

is equal to about 250~350 ml in modern society， and half

bei

is 125~175 ml. This study can provide a reference for further investigation of prescription dosage in bamboo and silk medical books before Qin Dynasty.