Cardiac mucinous neoplasm is the most common primary tumor of the heart in clinical practice, mostly benign and rarely malignant. Mucinous tumors can occur in the endocardial surface of all hearts, 95% in the atria, about 75% in the left atrium, 20% in the right atrium, and 2.5% in the left and right ventricles. Mucinous tumors in the left atrium often occur near the fossa ovalis. Clinically, they often block the mitral valve orifice, resulting in stenosis or complete closure of the mitral valve orifice. Clinical manifestations: The clinical manifestations of this disease depend on the location, size, and nature of the tumor and the presence or absence and length of the tip. The clinical manifestations of this disease depend on the location, size, nature, presence or absence of tumor and its length. If the left atrial mucinous tumor obstructs the pulmonary vein or mitral valve orifice, it may cause pulmonary stasis symptoms similar to mitral valve lesions; paroxysmal nocturnal dyspnea, hematochezia, jugular vein anger, hepatomegaly and swelling of lower limbs. Right atrial mucinous tumors that obstruct the vena cava and tricuspid valve orifice may present with symptoms similar to those of pericardial effusion; jugular venous irritation, hepatomegaly, and edema. The obstructive symptoms of this disease have the characteristics of episodes with position changes, such as position-related episodes of vertigo and dyspnea, and sudden fainting or cardiac arrest may occur when the tumor suddenly blocks the atrioventricular valve orifice and causes a significant decrease in heartbeat volume. 2. Embolism: Embolism of body and pulmonary circulation can occur when mucinous tumor fragments or tumor surface thrombus is dislodged. Embolism occurs in about 40% of left atrial mucinous tumors and is rare in right atrial mucinous tumors. Systemic symptoms: Fever, increased sedimentation, anemia, weight loss and abnormal increase of serum α2 and β globulin, which may be related to hemorrhagic necrosis and inflammatory cell infiltration in the tumor. Diagnosis and diagnostic basis: 1. Clinical features; obstructive symptoms, changes in heart sounds and murmurs. 2.Echocardiography is the best method to diagnose intracardiac mucinous tumor, especially the two-dimensional echocardiography can clearly show the outline and activity of tumor. Cardiovascular angiography shows the occupying lesion in the heart cavity, but there are certain false positives, own echocardiography, cardiovascular angiography is less used. Treatment: This disease has the risk of sudden death, so the diagnosis should be confirmed as early as possible for the suspected patients, and after the diagnosis is clear, cardiac tumor resection should be performed as early as possible, which can get better results.