Partial transmit sequence (PTS) is a promising technique for reducing the high peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. In PTS, multiple candidate signals are generated and the optimal signal with the lowest PAPR is selected for transmission. One drawback of PTS is that parts of the candidate signals are strongly correlated so as to degrade the PAPR reduction performance. The other is the high complexity. In this paper, an improved scheme is presented to reduce the correlation among the candidate signals, so as to improve the PAPR reduction performance. Furthermore, a threshold is introduced to reduce the complexity. Theoretical analysis and simulation results show that the new scheme can achieve higher PAPR reduction but with reduced complexity compared to conventional PTS.