This paper introduces the experience of Professor Liu Jiaxiang, a master of traditional Chinese medicine, in treating gastric cancer after surgery. It is considered that the pathogenesis is weakness of spleen and stomach, injury of both qi and yin, and lingering of pathogenic toxin. The dual deficiency of spleen and stomach can be seen throughout the disease process, and the influence of deficiency of stomach yin on the disease is emphasized. On the basis of “strengthening body resistance and treating cancer”, the method of supplementing qi and nourishing yin is used. Sijunzi Decoction and Yiwei Decoction as the main prescription, which can be modified clinically, can effectively prolong the survival time of patients. Two cases were exemplified to advocate the therapeutic thinking.