Abstract: In order to get optimum phase weighting factors, Partial transmit sequence method (PTS) requires the exhaustive search over all combinations of the allowed phase factors, and the search complexity increases exponentially with the number of sub-blocks. To solve this problem, two improved partial transmit sequence methods (Flipping IPTS and Threshold IPTS) are presented. In our methods, a cyclic shift of the Fast Fourier Transform (FFT) in the time domain is employed to improve the PAPR reduction performance. Furthermore, the paper makes use of iterative flipping algorithm to reduce computational complexity. The search complexity of the iterative flipping IPTS increases linearly with the number of sub-blocks. In order to reduce the computational complexity dramatically, a threshold is introduced to reduce the complexity. The theory shows the computational costs of PTS, PTS/CSS and proposed methods. The Matlab simulation results show that when the same number of sub-blocks and phase weighting factors, the proposed two IPTS methods have similar performance as PTS/CSS method with lower computational complexity, and achieve better performance than PTS method with comparable computational complexity.