Traditional high step-up voltage gain DC/DC converters suffer from a number of disadvantages such as large volume，high power devices voltage stress and limited voltage-conversion ratio.This paper proposes a novel high step-up voltage gain DC/DC converter without transformer component for photovoltaic power generation micro-inverters.Firstly，this paper discusses the operating conditions under continuous and discontinuous conduction modes，analyzes the principles of steady-state operating status，and outlines the voltage-conversion ratio and external characteristics of the converter.Secondly，this paper compares the proposed converter with traditional converters in view of voltage-conversion ratio，voltage stress and inductor current.A prototype converter rated at200W has been built in the lab.Experimental results of this prototype validate the design.