The grid-based Eulerian methods have dominated the CFD (Computational Fluid Dynamics) for decades due to its simplicity. The grids not only used for discretize the simulation domain but also used for the computation, however, due to the inherent disadvantages of the grid-based Eulerian method, the free surface flow cannot be simulated successfully without special numerical techniques. Recently, another numerical approach has been developed for hydraulic simulation, namely, the particlebased Lagrangian approach. In this approach, the domain discretization as well as the simulation procedure differs from traditional Eulerian approach. gridless methods are typical Lagrangian based method, the basic simulation elements used to discretize the simulation domain become particles rather than grids in gridless method, which leads the capability of the gridless method in simulating free surface flow.