According to the problem which exists in H-bridge cascaded STATCOM start-up process in the stage of pre-charge, the process of pre-charge using the style of uncontrolled rectifier is analyzed. On this basis, a improved pre-charge control strategy is proposed. This strategy controls the pulses in the stage of pre-charge, enables STATCOM to absorb active power of the grid maximum, increases the DC voltage steady value in the stage of pre-charge and controls STATCOM in the whole start-up process. The simulation and experiment verify effectiveness and feasibility of improved pre-charge control strategy.