A novel dual-input DC-DC converter with a high gain and a low voltage stress is proposed, which consists of two upper and lower symmetrical coupled inductor Boost converters. It has two modes, i.e., single-and dual-input, in which one and two switching tubes work, respectively. The novel converter can increase its voltage gain by changing the turns ratio of the coupled inductor. A three-level structure is used at the output terminal, thus reducing the voltage stress in the switching tube and diode. The operation modes of the converter with single- and dual-input are analyzed, and its main working waveforms are given. Its voltage gain and the voltage stress in the switching tube and diode are also derived. In addition, the influence of leakage inductance on the voltage gain of the converter is analyzed. Experimental results verified the correctness of theoretical analysis.