Aiming at the problem that the performance of timing synchronization algorithm is poor under low SNR and is sensitive to frequency offset in the OFDM system, an enhanced algorithm is proposed. First, based on the property that the cross-correlation value of the CAZAC sequence with different root values is close to zero, a preamble sequence with centrosymmetric characteristics is designed, then a timing metric function insensitive to frequency offset is designed using symmetric correlation instead of delayed correlation based on the structure of the preamble sequence. Finally, timing synchronization is realized by capturing the peak value of the timing metric function. The results indicate that, compared with the existing algorithms, the proposed algorithm has a strong anti-frequency offset capability and better timing synchronization performance under low SNR conditions, and is suitable for communication systems with low-SNR and frequency offsets.