Abstract: Rainfall runoff simulation and flood forecasting of an ungauged small basin is a complex forecasting problem. In this paper, we introduced the Grid-and-Mixed-runoff-generation-and-Kinematic-wave-based Hydrological Model (GMKHM model) for flash flood forecasting of a small ungauged basin. For each hydrological cell based on DEM (Digital Elevation Model) and RS technique, the net rainfall after canopy interception and evapotranspiration calculations is used for runoff generation and separation module in the GMKHM model. The mixed runoff generation model is applied for runoff generation computation, and overland and channel flows are routed by one-dimensional implicit finite difference kinematic wave flow model. The GMKHM model and the Xin′ anjiang distributed hydrological model were employed to Dagou Basin of Jialingjiang River for flash flood forecasting test in the 2009 flood season. Results show that the two distributed hydrological models perform well, and the flood peak simulation accuracy of the GMKHM model is better.