Over the past century, the concepts, objectives, and approaches of water resources management have changed significantly. Since watershed is the natural unit for water resources management, this paper, through literature review, proposes to develop a watershed science that takes into full account development and implementation of policies, processes, technologies, and organizations for understanding, distributing, and improving the movement and characteristics of water resources to meet the multiple needs of human societies and ecosystems in a socially responsible, economically viable, and environmentally sustainable way. Core components of the watershed science are: ①inventorying, monitoring, and modeling; ②goal setting; ③water allocation; ④indicator setting and measurement; ⑤organization and decision making process；⑥feedback  analysis.