The seabed instability induced by the transient liquefaction when exposed to wave-current may threaten the safety of offshore structures. In this study, the Reynolds-averaged Navier–Stokes (RANS) equations with the k–ε turbulence model were used to imitate the fluid dynamics, and Biot's poro-elastic theory was used to simulate the transient seabed response. An in-house solver (porous-fluid–seabed–structure interactions–field operation and manipulation) integrating the flow model and seabed model with the finite volume method was developed. The present model was confirmed with published experimental results and then used to analyze the dynamic process of the fluid–seabed–structure interactions as well as seafloor liquefaction around the jacket foundation under wave-current loading. The simulated results showed that the depth and range for the liquefaction area around the jacket foundation tended to increase at first and then declined as the wave propagated forward in the absence of current. In addition, the results demonstrated that the liquefaction depth under current and wave in the same orientation was greater than that without current. It is worth mentioning that the downstream piles were more prone to liquefaction than the upstream piles when the forward current existed.