Abstract: With the increase of voltage and power levels, parallel current source converters（CSCs） are widely used in the expansion of medium-voltage high-power current source systems. In order to solve the two problems of unbalanced DC bridge arm current and high common mode voltage in parallel current source systems, a five-level selective harmonic elimination（5L-SHE）modulation method for high-power parallel current source converters is proposed, which simultaneously achieves DC bridge arm current balancing and common mode voltage reduction, and ensures the power quality of grid current at low switching frequency.Firstly, the switching states of parallel CSCs are classified according to the norm of pulse width modulation（PWM） current, and the common mode voltage corresponding to each switching state is calculated. Secondly, the current balancing control strategy is established based on the influence analysis of the redundant switching states on DC bridge arm current. Thirdly, the switching state with lower common-mode voltage is selected to construct the 5L-SHE waveform, and the corresponding redundant switching state is reasonably selected according to the current balancing strategy. Finally, the effectiveness of the proposed method is investigated through simulation and experiment.