Objective　To the clinical characteristics, diagnosis and treatment of cardiac K-M syndrome. Method　The clinical data of cardiac Kasabach-Merritt syndrome (K-M syndrome) in an infant were retrospectively analyzed and the related literature was reviewed. Results　A 33-day-old boy presented with polypnea, jugular venous distention and low cardiac sound. Color doppler echocardiography and chest CT indicated massive pericardial effusion. Blood routine showed a decrease in platelet count. Patient was treated with acute partial resection of pericardium and drainage. Intraoperative findings included a 6 cm × 5 cm fixed firm mass on the surface of ascending aorta root, superior vena cava, the upper edge of right atrial appendage, and long strip protruding hard fixed mass seen in the right ventricular outflow tract and main pulmonary artery. Pathological findings in partial tumor of right ventricular surface and parietal pericardium showed Kaposi's hemangioendothelioma. The infant was diagnosed with cardiac K-M syndrome. The steroid therapy was administered. Conclusion　Cardiac K-M syndrome is a rare disease and is primarily diagnosed by clinical manifestations, imaging and pathological examination. It can be treated by oral steroid hormones and surgery if necessary.