Building a unified national market is a crucial support for constructing a new development paradigm and promoting high-quality economic development. Based on the strategic background of the unified national market, this paper takes the national e-commerce demonstration city policy as a quasi-natural experiment, utilizes panel data from 286 prefecture-level cities spanning from 2006 to 2023, and combines the staggered DID and double/debiased machine learning (DDML) to systematically evaluate the impact of this policy on economic growth in local and surrounding areas. Furthermore, starting from the theoretical framework of “five unifications”, it reveals the multidimensional mechanism through which the policy promotes market integration and regional coordination.

The study finds that the e-commerce demonstration city policy has a significant and sustained promotion effect on local economic growth. The policy exerts a positive spatial spillover effect on cities within a 200-kilometer radius, and the intensity of the impact diminishes with increasing geographical distance. Mechanism testing indicates that the policy primarily promotes the construction of a unified national market through enhancing market competition, optimizing supply chain efficiency, improving the business environment, and facilitating labor reallocation. However, the roles of regulatory oversight and capital allocation are not yet significant. Extensive analysis further reveals that the policy has a positive driving effect on real economy investment, labor demand, and technological innovation. This paper provides systematic empirical evidence for understanding the institutional functions of e-commerce policies in smoothing domestic circulation and promoting coordinated regional development. It also offers important insights into deepening integration of the real economy and the digital economy, as well as optimizing regional policy design.