The invention provides a method and a device for suppressing bridge arm circulation current of a modular voltage source converter, which relate to the field of flexible DC transmission. The method ofsuppressing bridge arm circulation current of a modular voltage source converter comprises steps: bridge arm current and output current of the modular voltage source converter are acquired, wherein the bridge arm current comprises upper bridge arm current and lower bridge arm current; according to the bridge arm current, the output current and a bridge arm circulation current formula, the bridge arm circulation current is determined, wherein the bridge arm circulation current formula is determined based on the relationship among DC, the bridge arm current and the output current; and accordingto a preset feedforward control algorithm, the bridge arm circulation current is controlled to determine feedforward control signals, the feedforward control signals are added to reference voltage ofthe modular voltage source converter, and thus, the bridge arm circulation current of the modular voltage source converter is thus suppressed.