The causes of pediatric mitral valve malformation are as follows: 1, congenital factors: mitral stenosis and incomplete closure due to valve dysplasia and subvalvular structural dysplasia. or regurgitation of the mitral valve and tricuspid valve due to other causes; 2, rheumatic changes in the valve: resulting in mitral valve closure insufficiency or mitral stenosis, and subacute bacterial endocarditis, resulting in the formation of a redundant mitral valve, affecting the closure and opening of the valve and forming damage to mitral valve function, all of these patients need early treatment.