A timing synchronization algorithm based on a pseudo-noise (PN) sequence is proposed aiming at the problems of sub-peak interference and timing instability at low signal-to-noise ratio (SNR) in the traditional timing synchronization algorithms. The structure of the training sequence is reconstructed and the calculation method of the timing measurement function is optimized by utilizing the good delay correlation and symmetric correlation of the PN sequence. The simulation results show that only one peak can be seen in the timing metric estimation curve and the sub-peaks are suppressed by using the proposed algorithm. The algorithm can realize accurate and stable timing synchronization, even when the length of the cyclic prefix is a quarter of the symbol length and the SNR is low.