Abstract: PAPR (peak-to-average power ratio) is the basic barrier to the practical application of OFDM system. To solve this problem, a novel PTS (partial transmit sequence) algorithm based on improved simulated annealing PTS (IMSA-PTS) is proposed, where the improved SA optimization approach is used to search the optimal combination of phase factors so as to avoid the local minimum due to the search for phase factor and acquire the minimum PAPR signal from all the states occurring in exhaustive search with unchanged simulated annealing process. Simultaneously, a threshold value is set to improve the convergence rate so as to reduce the computational complexity significantly. Simulation results showed that the proposed algorithm can provide favorable PAPR reduction with low computational complexity.