1. Objectives: This research was proposed to find out the selection and form of addition and subtraction of the Sasang prescription. 2.Methods: The related contents of the pathology and the medical action of a Sasang disease were selected in "Donguisusebowon- Sasangchobongyun, -Gabobon, -Shinchukbon(東醫壽世保元-四象草本卷, -甲午本, -辛丑本)", "Donguisasangsinfyun(東醫四象新編)". 3.Results and Conclusions: 1) The change and development of the Sasang prescription. 2) The selection of drugs are caused by immunity of the ordinary times and a class of present disease. 3) Addition and subtraction of the Sasang prescription can divide 4-type.