Abstract: An imposed pseudo-random sequence OFDM structure used in Time Domain Synchronization（TDS） is proposed，a timing synchronization which is exactly in the first channel delay by several periodically imposed short sequences and a long sequence is proposed.Each channel path estimated value of Minimum Mean Square Error（MMSE） is deduced by using periodical short sequences，in depth fading channel，the MMSE estimation brings the performance increase.Simulation results show that the proposed timing synchronization and channel estimation algorithm achieve good performance when imposed relative power is approximately 0.1.