Gastric cancer is one of the most common malignant tumors encountered in clinical practice, which seriously threatens human life and health. Studies have demonstrated that the occurrence of gastric cancer is associated with bacterial and virus infections, and epigenetic changes, especially changes in DNA methylation, play important roles in the progression of gastric cancer. Furthermore, DNA methylation detection has wide prospects for application in early diagnosis, prognosis assessment and treatment of gastric cancer. Hence, the authors address the relationship between DNA methylation and gastric cancer and the clinical applications.