A photovoltaic power generation system includes an inverter, a controller, and at least two direct current branch circuits. The leakage current detection apparatus is configured to: detect a leakage current of the direct current branch circuit on which the leakage current detection apparatus is located and send the leakage current to the controller. The controller is further configured to: when the photovoltaic power generation system runs and a value of a leakage current of the direct current branch circuit exceeds a preset range, determine that an insulation fault occurs on the direct current branch circuit. The system can determine the direct current branch circuit on which the insulation fault occurs in the photovoltaic power generation system, so that measures are taken in time for the direct current branch circuit on which the insulation fault occurs, to eliminate a potential safety hazard.