Aging has become a worldwide issue in the 21st century. China became an aging society in 1999, and home-based care is now the main mode of care for the elderly. Present research on the aging-suitability of spaces mainly focuses on the interior and exterior environmental conditions of the home, ignoring public open spaces at the regional and urban levels, with a specific lack of research on waterfront open spaces, which is an important type of public open space in Jiangnan Watertown. The study used the example of the waterfront space of the Hangzhou Gongchen Bridge section of the Grand Canal, the longest artificial canal in the world, to analyze the aging-suitability of waterfront open spaces. Firstly, in this section, the activity characteristics of the elderly were surveyed through observation and semi-structured interviews, then the subjective satisfaction of the elderly with the waterfront spaces was investigated. Through correlation and principal component analysis, five common factors affecting the satisfaction of the elderly were obtained: environment, function, transportation, social culture, and vision. Finally, some design suggestions suitable for the elderly were proposed for three aspects: environment, function, and transportation, which are the most important factors affecting the overall subjective satisfaction of the elderly with the waterfront open space. This study provided a reference for the design and planning of aging-friendly waterfront open spaces, which would improve the aging-suitability of urban open spaces, increasing social participation, and enhancing the quality of life of the elderly. It is of profound significance to build a senior-friendly city and deal with the increasingly severe aging problem.