Pepsinogen I and II, writing pepsinogen I and pepsinogen II in clinical examination, can be abbreviated as PGⅠ and PGⅡ, which are pepsin synthesized and secreted and transformed by gastric main cells and have the ability to break down protein. It can detect H. pylori infection, atrophic gastritis and gastric cancer and other gastric diseases, and is important in the early diagnosis of gastric cancer, and can be used as a monitoring index in the treatment process: 1. Diagnostic index: Since PGⅠ and PGⅡ are closely related to the surface area of gastric fundic mucosa, and PGⅠ and PGⅡ are more sensitive to gastric diseases, when gastric diseases occur in human body, PGⅠ and PGⅡ can appear to decrease. Therefore, joint detection of serum PGⅠ and PGⅡ levels, as well as serum PGⅠ and PGⅡ, can be used as suitable and reliable diagnostic indicators for determining chronic atrophic gastritis, and even gastric cancer, and also often used as screening indicators for early gastric cancer; 2. Monitoring indicators: such as superficial gastritis, erosive gastritis and other gastric diseases, serum PGⅠ and PGⅡ will increase and return to normal after cure. Atrophic gastritis, intestinal chemosis, heterogeneous hyperplasia to the development of gastric cancer, there will be a decrease of PGⅠ in serum, and the ratio of PGⅠ to PGⅡ becomes smaller. While in the occurrence of gastric ulcer and duodenal ulcer, the levels of PGⅠ and PGⅡ in the serum are increased to different degrees, which can return to normal after healing. Therefore, PGⅠ and PGⅡ can also be used as monitoring indicators in the treatment process.