The four ingredients of Siwu Decoction refer to Angelica sinensis, Ligusticum Chuanxiong, Radix Rehmanniae Preparata and Radix Paeoniae Alba. Among them, Paeonia lactiflora is bitter and slightly cold, and its taste is poor.

Siwutang is a classic medicated diet for enriching blood and nourishing blood in traditional Chinese medicine. It has the effects of enriching blood and regulating menstruation, and can relieve dysmenorrhea of women. Siwutang has been used in clinical practice of traditional Chinese medicine for thousands of years, and it is called the holy prescription of gynecology. Radix Rehmanniae Preparata and Radix Paeoniae Alba are tender and nourishing blood, while Radix Angelicae Sinensis and Rhizoma Chuanxiong are pungent and beneficial to qi.