Gastric cancer is one of common malignant tumors from a global perspective, and its morbidity ranks the forth and also the second largest cause of cancer-related death worldwide. Many factors can cause gastric cancer, including helicobacter pylori infection, chronic inflammation, genetic factors et al. Among all of these, helicobacter pylori infection can significantly increase the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in human stomach, which can cause the oxidative stress. Oxidative stress plays an important role in the pathogenesis of gastro-intestinal diseases such as mucosal damage, gastro-intestinal ulcers and cancer. Modern therapeutic treatments such as surgery and chemotherapy have undesired side effects, so the antioxidant therapy gains more and more attentions. Antioxidant therapy system comprises of various antioxidants (SOD, catalase, glutathione peroxidase and carnosine) and Chinese herbal medicine, which is mainly focused on the chemoprevention. Natural products and their derivatives, such as tea polyphenol, resveratrol and vitamins, have some potential benefits on their chemoprevention. Besides, much work has been done to understand the role of dietary factors playing in the prevention of gastrointestinal cancers. In this review based on some valuable studies, we aim to make some brief summaries about risk factors, pathogenic mechanism of oxidative stress and antioxidants therapy in gastric cancer.