The invention relates to cardiovascular systems, in particular to a digital simulation method for blood backflow caused by mitral valve insufficiency. A, a four-cavity lumped parameter angiocarpy dynamic circuit model equivalent to lesser circulation system, a systemic circulation system, a left heart circulation system and a right heart circulation system is established according to the equivalent relation of hemodynamics parameters and circuit parameters; B, according to the circuit model established in the step A, an established dynamic circuit is analyzed through a state variable analysis method, and corresponding state equations are established for related nodes in the circuit; C, according to simulation needs, the corresponding parameters in the step A and the step B are set, the state equations are solved according to the circuit model arranged in the step A and the state equations arranged in the step B, and the time curve graphs of the nodes in the circuit are obtained; D, QM obtained in the step C is calculated, and the blood backflow amount VRM, the mitral valve forward output amount VFM and the mitral valve volume VM under the condition that the mitral valve insufficiency occurs are obtained.