The invention provides a modular multi-level back-to-back current converter and a control method thereof, and relates to the technical field of power electronics. The modular multi-level back-to-back current converter and the control method solve the problems of great quantity of sub modules, structure complexity and the like of the existing modular multi-level back-to-back current converter. The current converter comprises six bridge arms, wherein the six bridge arms are in cascade connection to form a hexagon; the connecting ends of the adjacent bridge arms are sequentially set into three current flowing-in ends of the primary side of a three-phase alternating current system and three current flowing-out ends of the secondary side of the three-phase alternating current system in turns. The control method comprises the following steps of measuring/calculating a current reference value between any two ends in the current converter, and active current reference values and circulating current reference values of sub modules; calculating current reference values and voltage reference values of the sub modules; balancing the voltage of the sub modules in all the bridge arms. The modular multi-level back-to-back current converter and the control method provided by the invention have wide application prospects in aspects of large-scale wind power integration, power grid interconnection, electricity transaction, urban distribution network capacity increase, electric energy quality improvement and the like.