Abstract:Data market is the foundation of digital economy. Following General Secretary Xi Jinping's thought on promoting the classification, grading and separation of data, defining the rights and ensuring proper use of data, this study focuses on the main theoretical and practical issues of building data market by answering three questions which are why to build it, what to build, and how to build. It finds that the digital economy shows three-stages of development. With the enterprise data becoming dominant, it puts forward realistic requirements and offers development opportunities for data market. To overcome the obstacles in the way of building data market, it is necessary to start from the supply side, adhere to the top-level design, make full use of the market mechanism, and focus on solving the three problems of ownership definition, data supply, and transaction mode. Based on the theoretical research and practical needs, this study concludes with proposals to establish a national data administration bureau, a national data center, and a digital economy promotion law.