A photovoltaic system and a method for locating devices in a photovoltaic string. A communication host in the photovoltaic system acquires accumulated operation durations of MLPE apparatuses of the photovoltaic string, ranks the accumulated operation durations to obtain a ranking result, and determines a physical location of each device in the photovoltaic string according to the ranking result and a sequence of installing positions of the devices, where the devices are installed at the installing positions based on the sequence. It is not necessary to paste label codes on the MLPE apparatuses, or record serial numbers of the MLPE apparatuses by installation personnel. Operation processes are simplified, operation time is saved, and labor costs are reduced.