Traditional Chinese Medicine has its characteristics and advantages in the comprehensive prevention and treatment of malignant tumors. Based on long-time clinical practices and experimental studies, Department of Traditional Chinese Medicine of Changzheng Hospital of Navy Medical University (Second Military Medical University) established that "phlegm" is the core pathogenesis throughout the whole process of gastric cancer, and developed a theory of "phlegm syndrome of gastric cancer" and a series of prescriptions for eliminating phlegm. The therapeutic regimen based on this theory can significantly improve the quality of life and immune function and prolong the survival of patients with gastric cancer. This review introduces the theory of "phlegm syndrome of gastric cancer" and the treatment effect of eliminating phlegm prescriptions and drugs, elucidates their possible molecular mechanisms from the aspects of gastric cancer cell proliferation, apoptosis, epigenetic abnormalities, metastasis and tumor microenvironment, hoping to deepen the understanding of traditional Chinese medicine in comprehensive treatment of gastric cancer.