Abstract: Taking the string type photovoltaic inverter as the background, starting from the system composition and guided by the design goal, the string design, arrangement design, inclination design, spacing design, cable laying design, photovoltaic subarray design were expounded. Then, by analyzing the unit electrical topology and unit communication topology, the unit system cost and refined design value are obtained, and the refined design of the photovoltaic power generation system based on string inverter is expounded in the whole process.