Abstract: Seabed instability is often caused by seabed liquefaction. According to previous studies, the effective stress will remain in the silty soil after liquefaction. However, there have been little studies on the effective stress for wave-induced liquefaction up to date. In this paper, the pore-water pressures were measured for each depth in both cases of no liquefaction and liquefaction under different waves using the water flume as a tool and the results are compared and analyzed. The experiment results show that the relative value of the effective stress obviously decreased in the liquefied soil comparing to the non-liquefied. The effective stress shows a significantly difference in depth, and the difference decreases with the increase in wave height. There is a high effective stress after a certain time of liquefaction at the same depth and under the same wave, and then the effective stress decreases.