Abstract: In this study, a novel decoupling control scheme is proposed to solve the balance control problem of flying capacitor (FC) voltage and settle the decoupling issue between FC voltage and output voltage in three-level buck converters. We also establish an affine nonlinear mathematical model of the three-level buck converter and study the decoupling conditions of model linearization based on differential geometry theory. In addition, we derive a feedback control law of the decoupling subsystem, design a state feedback controller, and discuss whether the control parameters meet the stability requirements. Our simulation results show that the proposed control scheme has stronger anti-interference performance, faster response speed, and better dynamic regulation characteristics compared with the existing decoupling control method. The experimental results further verify the correctness and superiority of the proposed novel decoupling control scheme.