In the context of building a new development pattern, promoting inter-regional capital flow and realizing the integration of regional elements through digitalization is an important part of smoothing the domestic circulation and building a unified national market. The trans-regional investment data of China's A-share listed companies from 2010 to 2021 was collected, and a multi-time point DID model was constructed to empirically test the impact and mechanism of network infrastructure construction on the inter-regional capital flow. The results show that the construction of network infrastructure significantly promotes the inter-regional capital flow, and the core conclusions are still stable after considering factors such as endogeneity and other policy interference. The mechanism test shows that the network infrastructure construction promotes the inter-regional capital flow by improving the digital management level of enterprises and alleviating the information asymmetry of enterprises. Heterogeneity analysis shows that the promoting effect is more significant for non-state-owned enterprises, enterprises with high financing constraints, and enterprises with high market segmentation. From the perspective of enterprise capital flow, enterprises invest more across provinces than in different cities in the same province. It provides a useful reference for how to better release the dividends of the digital economy and accelerate the construction of a unified national market.