Heavy rainfall is the main catastrophic weather in Longnan city，Gansu Province. The disasters caused by heavy rainfall do great harm to social and economic development and people's life and property. In this paper，the processes of the two strongest rainstorms since 1961 in Longnan city，"7·22" in 2024 and "8·14" in 2020，are taken as examples. Based on meteorological，disaster situation and geographic information data，the disaster causing processes of the two rainstorms and heavy precipitation are analyzed and compared by using the theory of natural disaster system. The results show that："7·22" and "8·14" rainstorm processes have strong precipitation intensity，large cumulative rainfall，long duration of heavy precipitation and obvious extremity，which overlap repeatedly with the previous rainstorm areas，and are the main causes of disaster caused by "7·22" and " 8·14" rainstorm processes. The population and economic losses caused by "7·22" and "8·14" rainstorm and heavy rainfall accounted for 8. 5%，6. 5%，35. 8% and 45. 2% of the total population and GDP of Longnan city， respectively. "8·14" rainstorm and heavy rainfall disaster was significantly more serious than "7·22". The two process rainstorm disaster levels of severe grade occurred in Wudu district and Wenxian county，which are eco‐ nomically strong and populous in Longnan city. In the 9 counties of Longnan city，Wudu district and Wenxian county have the most hidden geological disaster points，the average slope and river network density are large， and the risk of disaster caused by heavy precipitation is high. As a result，the precipitation of Wudu district and Wenxian county is not the largest during the two heavy rains of "7·22" and "8·14"，but the disaster is the heaviest.