—In this paper, a novel peak power reduction scheme based on trellis shaping is proposed for single-carrier pulseshaped phase shift keying (PSK) systems. The use of PSK generally results in relatively low signal dynamic range, but its peak-to-average power ratio tends to increase as the bandwidth of pulse shaping filter becomes narrower. The simulation results demonstrate that the proposed approach can generate signals with almost constant envelope, even with the existence of pulse