Abstract: A high peak-to-average ratio (PAPR) and sensitivity to timing offset are typical in orthogonal frequency division multiplexing (OFDM) systems. The application of coding technology can address these problems effectively. Therefore, based on the complete sequence and the Hadamard orthogonal matrix, combined with a new mapping relationship, a new method for constructing 16-QAM periodic complementary sequences is proposed. This method can directly generate a sixteen-array sequence from a binary sequence, and can flexibly generate a variety of complementary sequences with different parameters according to differences between the complete sequence and the Hadamard orthogonal matrix parameters. The generated sequence has good correlation characteristics, which can effectively reduce the PAPR in the system. At the same time, based on the novel complementary sequence, in this study, a training sequence is designed in combination with the CAZAC sequence, a conjugate symmetrical structure is adopted, and an improved synchronization algorithm with lower complexity is proposed. The simulation results show that compared with the classical synchronization algorithm, the improved algorithm can still achieve correct synchronization under the condition of a low signal-to-noise ratio, the secondary peak has less influence on the main peak, and the root mean-square error is small, which can improve the accuracy of the system timing.