The construction of a unified national market is an important driving force for China's economy to achieve long-term high-quality development, and the digital economy is a key force in smoothing circulation and integrating factors. Based on China's provincial panel data from 2011 to 2020, this paper conducts empirical tests based on the theoretical analysis of the influence mechanism of digital economy in promoting the construction of a unified national market. Empirical results show that the digital economy significantly weakens the degree of interprovincial market segmentation and promotes the formation of a unified national market. From the perspective of operation mechanism, the digital economy can promote the construction of a unified domestic market by empowering the development of the circulation industry. The threshold model shows that the development of digital economy and circulation industry has a threshold effect on the positive impact of promoting the formation of a unified domestic market.