This paper assesses the emergency capacity of rain-flood disaster in provinces along the Yangtze River Economic Belt (YREB), China, from 2013 to 2017. In this study, the evaluation index system of emergency capacity on rain-flood disaster was built from the economic-social and environmental-natural aspects, and spatial auto-correlation analysis was used to analyze spatial differentiation characteristics of the emergency capacity. Then, the Spatial Durbin Model (SDM) was used to analyze the influence mechanism of the development level of economic-social factors (ESF) subsystem, environmental-natural factors (ENF) subsystem and the coupling level of these two subsystems on the emergency capacity of rain-flood disaster in provinces. The findings show that the emergency capacity distribution of rain-flood disaster in the YREB presented a “decreasing” spatial pattern of eastern, central and western regions. The development of two subsystems has produced spatial spillover effect and diffusion effect on the neighboring areas. There was a high coupling degree between these two subsystems in the YREB. Although spillover effect existed in space, the spillover did not depend on economic distance.