Abstract: Heavy rains often lead to large-scale floods disasters in river basins, which are disastrous to people living along the river basins and seriously hinder social progress and development. Based on the distribution of heavy rainfall, this paper selected four periods (2000, 2005, 2010, and 2015) of rainfall data in the Minjiang River Basin, and combining the analytic hierarchy process and geographic information system (GIS), a dynamic risk-evaluation index system and model was constructed from three aspects: disaster risk, disaster pregnancy sensitivity, and disaster-bearing vulnerability. The spatial distribution map of the dynamic risk of floods in the Minjiang River Basin was thereby obtained by ArcGIS. The results showed that: ① on the spatial scale, the variation of flood disaster risk results was consistent with the variation of disaster factors, and the spatial distribution of rainstorms was closely related to flood risk results. The high-risk areas were mainly in the southeastern plain of the Minjiang River Basin, and the low-risk areas were mainly in the northwestern region. ② On the given time scale, medium-risk areas dominated, and secondary-risk areas evolved from the lower-risk area to the higher-risk area, and the overall risk increased over time. These results reveal the relationship between the distribution characteristics of heavy rain and flood risk, which can not only effectively indicate the spatial distribution of flood disasters in the Minjiang River Basin, but also reflect the dynamic variations of flood risk, and provide a reference for disaster prevention and mitigation in the basin and thereby increasing social stability.