The measurement of ZHANG Zhongjing’s prescriptions and herbs followed the standards of weights and measures of the East Han Dynasty

in which the size of measurement of weight unit Liang（ 两） equaled approximately13. 8 g now. According to this calculation

dosages of herbs in the Han Dynasty were far more than ranges of herbs dosages allowed in Pharmacopoeia of People’s Republic of China. While in the Song Dynasty

with promotion and application of decoction powder（ 煮散剂）

there was a sudden decrease of dosages of herbs and prescriptions in clinical by a large margin. This article explores the reasons for large-scale prevail of decoction powder in the Song Dynasty

through analyses of medicine development and inheritance

factors of social

historical

political and economical background and advantages of decoction powder.