Abstract: To simulate the rainfall-induced flash floods in complex mountainous regions, a hydrodynamic model is developed based on the two-dimensional shallow water equations with rainfall and infiltration, and the Godunov-type finite volume method is used for numerical resolution. A new method of water depth reconstruction on sloping girds is proposed to resolve the problem of negative water depth and unphysical large velocity for simulation on complex topography. Numerical results of test examples show that the proposed model is stable and efficient, thus with bright application prospects.