An electronic device includes a radio frequency module having a communication port, and an antenna module having a number of antennas electrically coupled to the communication port. A method of reducing specific absorption rate (SAR) for the electronic device includes: a) measuring the SAR for the electronic device to obtain a measurement result; b) increasing the number of antennas of the antenna module when the measurement result is not lower than a standard value; and c) repeating steps a) and b) until the measurement result is equal to or smaller than the standard value.