Abstract: Scour around an offshore platform foundation is essentially a two-phase flow problem and can be predicted accurately by a two-phase flow model from the point of view of physical mechanics. In this paper, based on a two-phase flow model SedFOAM, a three-dimensional simulation of scour around an offshore platform foundation is conducted. The evolution process of the local scouring pit and the maximum scouring depth at the upstream and downstream of the pile foundation are investigated. The main influencing factors for the local scouring are analyzed. The results show that a semi-circular scouring pit appears at the upstream of the pile and the maximum dimensionless scouring depth is up to about 0.65 and is located at the upstream of the pile. During the scouring process, there is a deposition zone developing obliquely along the downstream of the pile. The scouring at the upstream of the pile is mainly affected by the submerged flow. The maximum scouring depth in front of the pile can reach 80% of the equilibrium scouring depth before the middle stage of the whole scouring process. The research findings can provide scientific basis for scouring prediction and foundation protection of actual offshore platforms.