In a transformer-less photovoltaic(PV) grid-connected power generation system, the transformation with a high voltage gain is realized by means of a non-isolated DC/DC converter between the PV cell and the grid-connected converter. In this context, a high-gain soft-switching DC/DC converter is proposed in this paper. Compared with the conventional Boost converter, this converter has advantages of a lower duty cycle, a smaller switching loss, and a lower voltage stress under the same voltage gain condition. Based on the analysis of the operating principle for the proposed converter, its performance is analyzed in detail. Finally, a 250 W prototype with 48 V input and 380 V output was built, and its highest measured efficiency was about 92.48%. Experimental results verified the correctness of the theoretical analysis.