Abstract: A method for simulation of a sway tank is presented,in which phase interface is treated as a physical discontinuity.The discontinuity is captured by a well-designed high order scheme.A numerical method for free surface flow on a fixed grid is established.This method is implemented in an in house code GTEA(General Transport Equation Analyzer) which is an unstructured grids finite volume solver.A classical dam break case and a two-dimensional rectangular sway tank at different excitation frequency are used to validate the method.The sloshing load on monitor points agrees well with experimental data.The method gives better results on the secondary peak compared with a commericial software CFX.It shows that the method simulates free surface overturning and breakup well.