Suction anchors are widely used in deep sea oil and gas engineering as a foundation for spars and TLPs because of their considerable uplift capacity and convenient installation.The suction anchor mainly sustains dynamic loads transmitted from the mooring line except for steady loads.The dynamic loads can be divided into two, wave-frequency loads with smaller amplitude and shorter period, and the second-order slow drift loads with larger amplitude and longer period.When the suction anchor is subjected to dynamic uplift loads with different frequencies and amplitudes, pore pressures increase in the soil around the anchor.In this study, to investigate the development of oscillatory pore-pressure and the accumulation mechanism of residual pore pressure in the seabed soil, a finite element model of a suction anchor embedded in a porous seabed subjected to dynamic uplift forces is constructed.On the basis of a steady uplift load, the pressure distribution and development under dynamic loads with different amplitudes and periods are contrasted.The results indicate that oscillatory and residual pore-pressure responses are significant around the anchor.Negative oscillatory pore-pressures mainly appear at the lower part of the anchor.Residual pore-pressure builds-up in the shallow soil, reducing the soil effective stress and the friction between the anchor and soil.Consequently, the failure mechanism may change and the uplift capacity is reduced.