Mitral stenosis is asymptomatic, which means it is not serious, and associated clinical symptoms and complications require targeted treatment. The main cause of mitral stenosis is rheumatic fever, and in its moderate stenosis, the mitral valve orifice area is 1-1.5 square centimeters, at which time there may be weakness, shortness of breath, and even dyspnea, etc., which may lead to atrial enlargement, atrial prematureness, atrial fibrillation, and other arrhythmias, and panic, etc., to determine whether it is serious and whether treatment is needed, which should be based on the presence or absence of acute rheumatic fever and related symptoms. The decision should be based on the presence or absence of acute rheumatic fever and related symptoms: 1, if there is a non-acute rheumatic fever attack and no symptoms, the condition is mild and may remain unchanged for several years, no special treatment is needed for the time being, and follow-up should be performed every 1-2 years. 2, if there is acute rheumatic fever or rheumatic fever recurrence, active treatment should be provided to prevent further aggravation of the valve lesion or even involvement of other valves, and to prevent the formation of perivalvular redundancy and dislodgment, causing cerebral infarction and other arterial embolism. 3, if the valve moderate stenosis with associated symptoms or new-onset atrial fibrillation, and there is no contraindication to surgery such as intra-atrial thrombosis, mitral valve balloon dilatation is feasible.