Abstract: Liquefaction under wave action is mainly caused by the pore pressure of seabed sediment. The mechanism of responding process of soil pore pressure to wave action is critical important to the understanding and prediction of liquefaction. The seabed silt pore pressure has been monitored for a long time in the Yellow River delta using the self developed pore pressure monitoring equipment. Monitoring results show that the change in pore water pressure is mainly determined by wave. And wave acts in a certain range, and there is no influence out of the range. Weather liquefaction was judged based on the change in pore water pressure in the monitoring process. Upon the above, the effect of wave action and the influence factors of liquefaction are discussed. There are three kinds of wave effects on pore pressures of seabed silt: a. there is pore pressure oscillation but no accumulation; b. there is pore pressure oscillation as well as accumulation; c. there is no pore pressure oscillation and accumulation.