Abstract: With the deepening of regional economic integration, transregional industry-related loss has become an important part of disaster loss assessment. Accurately quantifying the radiation impact of flood loss plays an important role in formulating disaster prevention and mitigation measures and reducing flood loss. Based on the systematic assessment of the loss from production shutdown or reduction under different rainstorms recurrence periods in Shanghai, this study adopted the two-region input-output model to calculate and analyze the intra-regional multiplier effect, inter-regional spillover effect and inter-regional feedback effect of different provinces of the lower reaches of the Yangtze River, and quantified the radiation impact of flood disaster loss in Shanghai on the lower Yangtze River region. The results show that with 10 a, 20 a, 30 a, 50 a, and 100 a return period of rainstorm, the loss from production shutdown or reduction in Shanghai is 1.401 billion yuan, 1.983 billion yuan, 2.558 billion yuan, 3.382 billion yuan and 4.624 billion yuan, respectively. In the lower reaches of the Yangtze River, Anhui Province has the largest economic linkage, Shanghai and Zhejiang Province have the largest economic interaction, and the inter-regional industrial linkage loss is dominated by spillover effect. In the event of flood disaster in Shanghai, the cross-regional spread effect will lead to 26.24% increase in losses in the lower reaches of the Yangtze River. Therefore, in today's increasingly close relationship between cities, we should not only pay attention to the impact of flood disasters on ourselves, but also take effective measures to reduce the spread impact between regions, so as to more effectively carry out disaster prevention and reduction work.