The embodiment of the invention discloses a method for improving efficiency of an orthogonal frequency division multiplexing OFDM communicator and a device thereof. The method comprises the following steps: acquiring a predictive value of a peak average ratio PAR of an intermediate frequency output signal, according to resource distribution condition; acquiring a PAR margin, according to the PAR predictive value of the IF output signal and a PAR index of an OFDM system; and adjusting power supply voltage of a radio frequency power amplifier, according to the PAR margin. The embodiment of the invention adjusts the power supply voltage of the radio frequency power amplifier through predicting PAR of the intermediate frequency output signal, thereby effectively improving the efficiency of the OFDM communicator.