The invention discloses a simultaneous frequency-doubled and frequency-quadruplicated loop current suppression method suitable for an MMC (Modular Multi-level Converter). The method comprises the steps of extracting current values of upper and lower bridge arms of each phase of the MMC, and calculating a loop current value according to the acquired current values; performing frequency-doubled negative sequence and frequency-quadruplicated positive sequence rotating coordinate transformation on the calculated loop current value to transform frequency-doubled and frequency-quadruplicated components into direct-current components respectively; comparing dq axis components of the transformed frequency-doubled and frequency-quadruplicated components of the loop current with a corresponding loop current dq axis component reference value respectively, and then performing linear adjustment control; introducing voltage feed-forward quantities corresponding to the frequency-doubled and frequency-quadruplicated components to eliminate a dq axis coupling part, then obtaining a dq axis reference value for loop current suppression, performing frequency-doubled negative sequence and frequency-quadruplicated positive sequence inverse transformation on the obtained dq axis reference value respectively, adding the obtained corresponding loop current suppression reference values, and adding the sum to a modulated wave signal. The reference value obtained by frequency-doubled negative sequence rotating coordinate transformation on loop current can effectively suppress second harmonic in the loop current.