The invention discloses a multi-step model forecast control-based circulation control method of a modular multilevel converter (MMC). The circulation control method comprises the following steps of firstly, performing dead beat control by an AC output current of the MMC to obtain reference input module numbers of an upper bridge arm and a lower bridge; secondly, performing single-step circulation forecast by combining a circulation current discrete state equation; thirdly, selecting the input module number conforming to a single-step forecast effect, and performing multi-state circulation forecast; and finally, solving an optimal solution of the bridge arm input module number, and achieving multi-step optimal control of a circulation current so that a harmonic current in the circulation current is effectively suppressed. The circulation control method comprises AC dead beat control, circulation single-step forecast and circulation multi-step forecast. Aiming at the circulation harmonic current of the MMC, a multi-step forecast finite control set is built by a multi-step model forecast control method according to the optimal solution obtained by single-step forecast, the cycle forecast frequency required by multi-step forecast can be substantially reduced, and the calculation quantity of a controller is effectively reduced.