Si Wu Tang, which consists of Danggui, Shaoyao, Dihuang and Chuanxiong, was first recorded by the Tang Dynasty doctor Lin Daoren. In his book, the dosage of the four Chinese herbs were the same and the formula was used to treat injury-caused blood stasis in the intestinal tract. As time passed, the dosage of herbs in Si Wu Tang had been modified. Gradually, Si Wu Tang has become a common formula for gynecological disease. In this study, we analyzed the relationship between the dosages of herb in Si Wu Tang and Blood-deficiency and Blood-stasis patterns. The results found that Chuanxiong played an role when Si Wu Tang was used to treat Blood-stasis pattern.