The 5th generation mobile networks (5G) and their key technologies need to provide higher spectrum efficiency utilization and smooth integration of broadband and narrowband systems. Filter bank multi-carrier transmission with Offset Orthogonal Amplitude Modulation (FBMC-OQAM) has great advantages to achieve this goal by combating multipath effects and offering high-speed data rate in wireless channels. In this paper, an improved partial transmit sequence(PTS) scheme employing particle swarm optimization (PSO) algorithm is proposed to reduce the peak-to-average-power ratio (PAPR) of the FBMC-OQAM system. Compared with the conventional PTS scheme, the proposed scheme takes the overlapping structure of FBMC-OQAM signal into account, and develop a segmentation scheme based on windowing for the PTS scheme (W-PTS). To reduce the computational complexity, we further propose a PSO-PTS scheme, which significantly reduces the computational complexity. Simulation results show that the proposed scheme could provide a significant performance in PAPR reduction with a relative low complexity.