Abstract: Since cubic metric (CM) can more accurately predict the power de-rating of power amplifier (PA), it is recognized as a better metric to characterize the envelope fluctuations of orthogonal frequency division multiplexing (OFDM) signals than peak-to-average power ratio (PAPR). To improve the PA efficiency, a common scheme is minimizing the CM value of signals. However, this aggravates the in-band distortion, resulting in bit error ratio (BER) degradation of systems. This paper formulates the problem as an in-band distortion optimization subject to CM constraint, and a customized interior-point algorithm is developed to solve the optimization problem. Simulation results show that the proposed algorithm provides better BER and CM-reduction performance than existing optimization schemes.