In order to further understand the characteristics and causes of the autumn floods in Weihe River, this paper uses the flow and meteorological data of the flood happened in Weihe River in September, 2019(2019.9 Flood) to analyze its characteristics and the meteorological causes of continuous heavy rainfall during the flood. The results show that the strong Arctic vortex in the northern hemisphere, flat circulation in the middle latitudes and relatively stable position and abnormally westward of the subtropical high pressure belt caused the continuous intersection between the cold and warm air over Weihe River, resulting in the continuous heavy rainfall. The water vapor of the rainfall came from the Arabian Sea and the Bay of Bengal, and the convergence of its flux appeared abnormal during the heavy rainfall. The flood mainly occurred in the tributaries between Linjiacun and Lintong with low sediment concentration, whereas heavy flow prevailed at the mainstream of Weihe River. The flood between Lintong and Huaxian proceeded slowly with long duration, and the flood peak was greatly reduced during the course.