T-type three-level inverter has been widely used in medium-voltage and high-power situations, but its own topological characteristics make it have the problem of midpoint potential imbalance. Based on the space vector pulse width modulation of T-type three-level inverter, this paper analyzes the influence of large, medium, small and zero vectors on the midpoint potential, and presents a control method of constructing virtual vectors and balancing the midpoint potential by using redundant small vectors and large vectors or zero vectors. Finally, the simulation results in MATLAB/Simulink demonstrate the effectiveness of the proposed method.