The invention discloses a control method for a photovoltaic power generation system and a photovoltaic power generation system. The photovoltaic power generation system comprises an optimization assembly string and an inverter. The optimization assembly string includes a plurality of optimization assemblies; the input terminal of each optimization assembly is coupled with at least one photovoltaicassembly and the output terminals of the plurality of optimization assemblies are connected in series. Each optimization assembly includes a control unit. The input terminal of the inverter is coupled to the output terminal of the optimization assembly string. The inverter includes an auxiliary detection module that is used for assisting in detecting the output current of the optimization assembly string. The control units are used for controlling the output voltage of the optimization assembly string according to the output current of the optimization assembly string, so that the output voltage meets the starting condition of the inverter.