Abstract：ZHENG Qin'an is a famous medical scientist in Qing Dynasty who is well known for using hot-natured herbs likes Zingiberis rhizoma recens and Aconiti lateralis radix praeparata. He attached importance to Yang of Kanzhong. Generally speaking，he believed that the basic pathogenesis of phlegm and retained fluid is yang qi deficiency. The failure of transfusion of body fluid leads to phlegm and retained fluid. He also pointed out that phlegm and retained fluid has a wide range of pathogenic factors and varies in many ways. In treatment，yang qi is first，expelling phlegm is last，and yang qi works well， phlegm and retained fluid disappear.