Abstract: At present, the flood inundation process analysis in a watershed under real-time rainfall cannot meet the needs of practical engineering application because of its complicated implementation procedure. Although the non-source inundation analysis method is highly popularized and is easy to implement, its actual physical significance is not strong. To this end, this paper aims at establishing a cellular automata-based flood inundation analysis model with the aid of real-time rainfall forecast and GIS technologies, in which the GIS technology is used to generate the raster data for digital elevation model. Then, the flood inundation area and water depth can be obtained according to the underlying surface conditions of the watershed. Finally, the Yuanzhou watershed in Yichun City, Jiangxi Province, is taken as a typical case for investigation, two kinds of rainfall losses, including vegetation interception and soil infiltration, are considered. The runoff coefficient is used to represent runoff loss process generated by rainfall. Then, the flood inundation data of Yuanzhou watershed at four different moments（10 minutes, 30 minutes, 1 hour and 2 hours） are evaluated by using the established cellular automata-based flood inundation analysis model. The results of the non-source inundation analysis method and MIKE SHE based-overland flow model are employed to validate the effectiveness of the established cellular automata-based flood inundation analysis model. The results indicate that the established model in this paper can well consider the influences of the underlying surface condition of the watershed and the rainfall production and confluence processes, and thus can simulate the flood inundation more reasonably and output the flood inundation data in real time, as compared with the non-source inundation analysis method and MIKE SHE based-overland flow model. The established cellular automata flood inundation analysis model has strong popularization and application prospects, clear practical physical meaning and simplified calculation process, and can accurately output the flood inundation process under a real-time rainfall event. The research outcomes can provide theoretical references for the risk assessment of flood disaster and the formulation of flood control and rescue decision plan under a heavy rainfall event.