Xiaohong River and the reservoir group in its upper and middle reaches together with the Yangzhuang flood detention area of Xiping County, and the Laowangpo flood detention area of Xiping County are important components of the flood control system of Huaihe River. The joint application of Xiaohong River flood control project has undertaken the key flood control tasks in the flood control work of southern Henan Province. Since 2008, the flood discharge capacity has enhanced remarkably with its urban water system treatment project. In this paper, the flood occurred in the Xiaohong River Basin on July 21-23, 2020 induced by heavy rain and rainstorm was analyzed from the aspects of rainfall, flood process, flood magnitude, flood propagation time and project flood control operation. Results suggest that the operation of upstream reservoir has an apparent influence on the flood of July 22. Guili Station witnessed anomaly in the relationship between measured maximum water level and maximum discharge and the guaranteed water level and discharge. The principle of full detention of flood is suggested to adjust the characteristic water level of Guili Station for flood control. The research finding offers a basis for precise flood management in the Xiaohong River basin.