Abstract: A non-isolated soft-switching high-voltage-gain quasi-Z-source DC-DC converter is proposed in this paper. The converter has the advantages of a continuous input current, a common ground for input and output, a high voltage gain, and low stresses of switching devices. At the same time, all the switches in the converter operate under zero voltage switching (ZVS) conditions, and all the diodes operate under zero voltage zero current switching (ZVZCS) conditions, which can reduce the switching losses of the switches and the reverse recovery losses of the diodes. By introducing a three-winding coupled-inductor, the voltage gain of the converter is improved, while the addition of an active clamp circuit reduces the voltage spikes at both ends of the switches. The coupled-inductor with a smaller inductance value corresponds to a smaller copper loss and volume, thereby improving the efficiency and power density of the converter. A thorough analysis of the working modes of the converter is conducted, and the voltage gain of the converter, as well as the voltage and current stresses of the components, is derived. Steady-state analysis and parameter design are carried out. Finally, a 100 kHz, 200 W, 38~380 V experimental prototype is built, and the efficiency of the converter at rated power is 96.13%. The experimental results are consistent with the theoretical analysis, indicating the feasibility of the proposed converter.