Abstract: Gastric cancer is one of the most common gastrointestinal malignancies and it has close relationship with the infection of H.pylori. The cytotoxin-associated gene A (CagA) of H.pylori has become a research hotspot for the study of the pathogenesis of gastric cancer. This study summarizes the pathological activities and its possible role in the occurrence of gastric cancer and discusses the relationship between CagA and gastric cancer.