In order to improve the refined management and planning of the Yangtze River shoreline, the definition method for the shoreline protection scope of the lower reaches of the Yangtze River is preliminary explored in this paper. Referring to the Yangtze River Protection Law as well as the relevant literatures, standards and regulations, a defining and planning method for the shoreline protection scope of the lower reaches of the Yangtze River is proposed. In this method, both the shoreline administration scope for hydrological departments and a “shoreline-riparian zone-buffer zone” based protection scope are considered comprehensively. For the riparian zone and buffer zone, they can be obtained in consideration with ecology and hydrological functions of shorelines and utilization modes of hinterland areas. Based on the Yangtze River coastline in the Yangzhou section, the application analysis of the proposed definition method indicates that this method has a good correlation with the current shoreline management methods and shows good operability. The proposed methods can provide a support for the formulation of the shoreline protection plan for the lower reaches of the Yangtze River.