The power transmission ability of a same converter can be expanded by improving the current utilization ratio of switching devices of modular multilevel converter based HVDC (MMC-HVDC), and hence the cost of converter of MMC-HVDC can be reduced. Based on the characteristics of MMC, this paper presents a new type of circulating current control strategy considering double frequency harmonic current injected, and gives mathematical deduction of amplitude and phase of the double frequency sinusoidal harmonic current injected. This new strategy can reduce the peak value of the arm current up to 20%, improve the current utilization rate of the converter, and enhance the power delivery capacity of the converter up to 25%. At last, the simulation model of MMC is established in RTLAB, and the new circulating current suppression strategy is carried out. The simulation results verify the accuracy and effectiveness of the proposed control strategy.