Typical area in Yellow River estuarine tidal flat is chosen and studied. The dynamic response process of saturated fine grain soil and the Penetration stress,peak strength,residual strength,the variation of sensitivity,and the influence of the variations of pore water pressure and the liquefied layer on the liquefied process of the silt soil in the area under cyclic loading are investigated and compared by real-time monitoring of pore pressure,static cone penetration test,vane shear test and the geotechnical test. Results show that the change of soil structure has close relations with the characteristic of energy absorption,the response of pore pressure under cyclic loading. The liquefaction of the silt soil in the area of Yellow River delta happens in hard crust mainly due to the cyclic loading. With the increase of the cyclic number,the liquefied layer extends to deep site. The changing tendency of the physical index of soil mass shows obvious difference with the change of depth due to the action of cyclic loading.