A method for transmitting wireless power in a wireless charging system is provided and includes receiving at least one of information on an available maximum temperature and maximum voltage value information of a back end of a rectification unit from at least one wireless power receiving unit (PRU) from among a plurality of PRUs, receiving at least one of information on a current temperature and current voltage value information of the back end of the rectification unit from each of the plurality of PRUs, and determining a dominant PRU among the plurality of PRUs based on the at least one of information.