Stage Ia gastric cancer indicates that the tumor invades the lamina propria, the muscular layer of the mucosa, or the submucosa. The histologic stratification of gastric mucosa includes mucosal layer, submucosal layer, muscular layer, and plasma membrane layer. Among them, the mucosal layer can be further divided into columnar epithelial cell layer, lamina propria, and muscular layer of the mucosa. Stage Ia gastric cancer is the clinicopathological stage, which refers to T1N0M0 in TNM staging, i.e. it means that the primary tumor invasion is still in the mucous layer or has invaded the submucosal layer but has not reached the muscular layer, and at the same time there are no lymph nodes and distant metastases. Stage Ia gastric cancer belongs to early gastric cancer, which can be treated by endoscopy or surgery according to the patient’s pathological staging and physical condition, and after surgery, regular review is needed to pay attention to the disease condition and timely symptomatic treatment.