The present invention discloses a directional solidification method for a superalloy single crystal blade based on solid-liquid interface steady control. The method establishes effective criteria for withdrawal speed adjustment, i.e. the related position between a macro solid-liquid interface and a thermal baffle, the range between the dendrite tips at the solid-liquid interface, and the difference between the advance speed of the macro solid-liquid interface and the withdrawal speed. With these criteria, the advance of the solid-liquid interface during directional solidification is simulated and a withdrawal speed curve v(t) for the solid-liquid interface steady advancement was obtained. And then, the single crystal blade was prepared.