A High Step-up DC/DC photovoltaic interfacing (HS) converter is proposed. It steps up the voltage by using a special structure, and the boost structure is composed of two inductors, a capacitor and two diodes. Combing the special boost structure with the double-switch boost DC converter, HS converter is obtained, which depends mainly on charging and discharging of the inductors and capacitors to realize the step-up function. In addition, (Repeated HS, Re-HS) and (Generalized HS, G-HS) converters are proposed. The voltage gain of the continuous conduction mode(CCM) was analyzed. The voltage gain, voltage stress and ripple current of HS converter was deeply studied and compared with other converters. In order to verify the correctness of theoretical analysis, the actual circuit of HS converter was built. The simulation and experiments show that the HS converter has the characteristics of high gain and low ripple.