Smoothed particle hydrodynamics (SPH) method is a fully Lagrangian meshless method, which is available to simulate the problems with instantaneous very large deformation, such as wave cracking, high-speed water flow, high-speed impact and collision. The basic principle,kernel function,discretization of governing equations and boundary treatment of SPH method are introduced, a numerical flume model is constructed and its validity is verified. 2D dam-break problem under two cases is simulated respectively, i.e. obstacle with and without holes, and the computational results are compared and analyzed. It is demonstrated that the SPH method can nicely capture the variation of the free surface flow, the fluid fragment and coalescence, and to some extent, the energy dissipation effect is better when the obstacle has holes.