The watercourse entering the Yangtze river is the largest flood discharge course in the lower Huaihe River, through which more than 70% flood from the upper and middle reaches of the Huaihe River enters the Yangtze River. According to measured data in flood period from 1961 to 2018, the flood discharge capacity and flood control capacity of the watercourse are calculated and analyzed using stage-discharge relation method. Results show that due to the limits of historical objective conditions and the difficulty and complexity of the regulation of four cascade control sections, the flood discharge capacity of each control section in different periods presents varied characteristics respectively. After years of continuous and effective governance, the flood discharge capacity has been improved overall. According to measured data in recent years, the flood discharge capacity of the four cascade control sections has met design requirements in general. The research finding offers reference for flood relief and threat reduction of catastrophic floods in the lower Huaihe River, and is of great practical significance for the sound and rapid development of economy and society in this region.