现今的淮河下游是指洪泽湖以下的入江、入海水道。广义上还包括沂沭泗水系、里下河地区水系和中运河、里运河。历史时期黄河、运河、淮河交汇于此,水流状况复杂,水利工程众多,地形和水系都发生了极大的变迁。在过去的近千年中,淮河下游变迁的发生、发展和变化构成了一个完整而典型的地理现象和地理过程。以前对淮河水系变迁、黄河南徙入淮和运河的变迁都有一定的研究,但相对于黄河的研究和运河的研究,对淮河的历史地理研究还是很薄弱的。笔者将淮河下游的变迁作为主题,将黄河南徙和大运河的变迁作为影响淮河变迁的因素来进行分析,探讨淮河下游水系变迁的规律, Today’s Huaihe River refers to the following Hongze Lake into the river, into the sea. In a broad sense, it also includes the Yishusawa River system, the Lixiahe area water system, and the Grand Canal and the Grand Canal. During the historical period, the Yellow River, the Grand Canal and the Huaihe River converged here. The flow conditions are complex, and there are many water conservancy projects. Both the terrain and the water system have undergone tremendous changes. In the past millennia, the occurrence, development and changes of the vicinities of the Huai River have formed a complete and typical geographical phenomenon and geographical process. Previously, there were some researches on the changes of the Huaihe River system, the southward migration of the Yellow River into the Huaihe River and the changes of the canals. However, compared with the research of the Yellow River and the research of the canals, the history and geography of the Huaihe River was very weak. The author takes the change of the Huaihe River as the theme, analyzes the changes of the south migration of the Yellow River and the Grand Canal as the factors that affect the change of the Huai River, discusses the law of the change of the water system in the lower reaches of the Huaihe River,