A new single-phase transformerless current source inverter is proposed in this paper. The proposed inverter can achieve leakage current reduction, which is crucial for the conventional current source inverter. The basic concept of the proposed solution is to develop the new inverter by the duality principle from the voltage source inverter. The theoretical analysis is carried out to determine the switching states of the proposed inverter for the leakage current reduction. Also, a new modulation strategy is presented to achieve the optimized switching states. Finally, the experimental results are presented. Comparing with conventional single-phase current source inverter, the leakage current can be significantly reduced by the proposed inverter, which verifies the effectiveness of the proposed solution.