A radio-frequency (RF) power amplifier includes a matching network comprising at least one matching network circuit corresponding to at least one symmetry node, at least one detector for detecting power of a detected signal at the symmetry node of the matching network, and generating at least one control signal according to the power of the detected signal, wherein the detected signal is an odd harmonic of an RF signal when the RF power amplifier operates in a differential mode or an even harmonic of the RF signal when the RF power amplifier operates in a common mode, and at least one adjusting circuit for adjusting the RF signal according to the at least one control signal.