Disclosed are an apparatus and a method for preventing the degradation of RF performance due to a change in impedance of an antenna in a mobile communication terminal. The mobile communication terminal includes a plurality of impedance matching circuits and a controller of the mobile communication terminal is adapted to measure the reflection voltage of the antenna, select one impedance matching circuit corresponding to the measured reflection voltage, and connected with the antenna through the selected impedance matching circuit. As a result, when the impedance value of the antenna is changed, it is possible to prevent the degradation of performance of the RF module of the mobile communication terminal by using an impedance matching circuit, which can optimize the reflection loss caused by the reflection voltage of the antenna according to a change in impedance value.