Nowadays, with the development of science and technology and medical level, many cancers can be detected through examination at early stage, such as early gastric cancer, gastroscopy is the first choice of examination. The advantage of gastroscopy is that it can detect early gastric cancer without symptoms in real time, and even some patients may be detected during physical examination, which can be clearly diagnosed through gastroscopy. If it cannot be seen clearly under gastroscopy, ultrasonic gastroscopy can be utilized or staining of gastric mucosa, such as Congo red or methylene blue staining, can be done during gastroscopy to differentiate between normal mucosa and abnormal mucosa through staining. Ultrasound gastroscopy can show the whole picture of the tumor inside and outside the gastric cavity at the same time, which can not only detect early lesions, but also understand the size and depth of the tumor. If there is no advanced technology in underdeveloped areas, gastrointestinal imaging or blood sampling can be performed to check tumor markers. Gastrointestinal imaging is only effective for late or middle gastric cancer, and it is not ideal for early diagnosis of gastric cancer. For patients with atrophic gastritis, pepsinogen can be measured, and the most basic and simple method is fecal occult blood, and patients with positive fecal occult blood should pay attention to it.