Abstract: In order to solve the problem of insufficient boost capacity of high boost non-isolated converters required in renewable energy system, a soft-switched high voltage gain quasi-YZ source DC-DC converter is proposed based on the advantages of Y source converter and quasi-Z source converter. The proposed converter can not only improve the voltage boost capacity, but also effectively absorb voltage spikes caused by leakage inductor. Furthermore, the application of synchronous rectification technique enables the switches and diodes to operate in soft switching condition and improves the conversion efficiency. In addition, the proposed converter has continuous input current and low current ripple due to the single inductor connected at the input voltage. Moreover, it has the advantages of low switch voltage stress and common ground between input and output voltages. First, the working modes and steady states of the proposed converter are analyzed. Then, efficiency and loss distribution are calculated quantitatively. The performance of the proposed converter is compared with other converters, and the design requirements are defined. Finally, the effectiveness of the proposed converter is verified by a prototype made in the laboratory.