Herein, we test the hypothesis that a member of a formulated Chinese herbal decoction cannot be replaced by another herb. Danggui Buxue Tang (DBT) is being used as an example for illustration: this is a traditional decoction containing Radix Astragali (RA) and Radix Angelicae Sinensis (RAS) in a weight ratio of 5 to 1. Rhizoma Chuanxiong (RC) and RAS are two chemically very similar herbs but with a distinct function. Following the preparation method of DBT, a herbal decoction, namely Chuanxiong Buxue Tang (CBT), was created, which contained RA and RC in a weight ratio of 5 to 1. The two decoctions, DBT and CBT, were compared in parallel regarding their chemical and biological properties. In all the tested parameters, DBT showed superior properties, both chemically and biologically, to that of CBT. The current results reveal the uniqueness of Chinese herbal decoctions that require a well-defined formulation, which is indispensable for its specific composition.