Abstract: The present application relates to a guide rail, a guide rail assembly, a photovoltaic assembly and a method for arranging the photovoltaic assembly. The guide rail is used for guiding folding and unfolding movements of photovoltaic panels of a foldable photovoltaic assembly. The guide rail comprises a guide rail body, wherein the top of the guide rail body is provided with a first rail extending in a lengthwise direction of the guide rail body, and a side face of the guide rail body is provided with a second rail extending in the same direction as the first rail. The guide rail can ensure smoother and more stable folding and unfolding movements of the photovoltaic panels, making it unlikely for the moving part to deviate from or fall off the guide rail. It can also enhance the connection strength between the photovoltaic panel assembly and the guide rail, and improve the overall stability of the photovoltaic assembly.