The pericardial cavity of the heart is clinically known as the pericardial cavity, of which those caused by cancer are known as malignant pericardial effusion, and the vast majority are caused by metastatic tumors. Common malignant tumors that easily metastasize to the pericardium include lung cancer, breast cancer, lymphoma, leukemia and so on. Tumor cell metastasis to the pericardium can cause capillary permeability increase, large amount of fluid exudation to form effusion, and most of them are bloody effusion after pericardiocentesis. Malignant pericardial effusion is similar to the formation process of pericardial effusion caused by other reasons. When the amount of effusion is large, it can seriously affect the diastolic function of the patient’s heart and even cause cardiac tamponade, which will cause the patient to suffer from acute heart failure, and it may lead to the patient’s death if it is not treated in time. Patients who have suffered from malignant tumors in the past and find that a large amount of pericardial effusion is formed in a short period of time should be suspected of being caused by malignant tumors, and it is recommended that they go to the hospital as soon as possible to have the nature of the effusion clarified in a timely manner and be treated accordingly.