Portable electronic device and power controlling method thereof

A portable electronic device includes an antenna, a transceiver module, a posture sensor and a micro processor. The transceiver module is coupled to the antenna, receives radio frequency signal from air interface via the antenna, and transmits radio frequency signal to air interface via the antenna. The transceiver module further receives a power control signal and adjusts a transmitting power of the antenna, accordingly. The posture sensor detects a current placement angle of the portable electronic device and generates a detection result, accordingly. The micro processor is coupled to the transceiver module and the posture sensor, for receiving the detection result from the posture sensor and generates the power control signal to the transceiver module according to the detection result.