[Objective] The characteristics of rainstorm flood disaster risk in main flood season were studied in Sichuan-Yunnan region to provide theoretical reference for defense of regional rainstorm and flood disasters. [Methods] Methods of inverse distance weighted interpolation(IDW) and natural disaster risk index were used. [Results] The highest risk area of rainstorm flood disasters was mainly concentrated in the eastern Sichuan Basin and the followed area was the southern part of Yunnan Province. Moderate-risk areas were mainly distributed in the southwest mountainous region of Sichuan Province and the most areas of Yunnan Province. Lower-risk area were sporadically distributed in East Yunnan Plateau, Northwest Yunnan Province and the northeastern part of Western Sichuan Plateau. The lowest-risk area was mainly located in Western Sichuan Plateau. [Conclusion] The main influence factors of rainstorm flood disasters were atmospheric circulation, precipitation, topography and river network; the change of land use due to human activities was the trigger of rainstorm flood disasters.