A voltage balancing control method based on single-carrier modulation is probed, in order to solve the capacitor voltage balance problem of cascade STATCOM. Aiming at the single-carrier modulation cascade STATCOM, voltage decoupling control is adopted to realize the control of overall active power. In terms of voltage balancing control, a voltage balancing control strategy which combines the energy exchange method and circulation transposition method is proposed to realize the voltage dynamic balance process by controlling the charge and discharge time of each link capacitor, and through pulse circulation transposition to improve the steady state balance precision. A switch control method is proposed to realize reliable switching of working mode, finally, the simulation results verify the effectiveness of the balance control method.