Winning the battle against key core technologies is a crucial measure to enable China to seize the commanding heights of technological development under the current “technology blockade” external environment. This paper constructs a market access index using geographical distance and GDP data， and examines its impact on key core technological innovation based on panel data of 280 prefecture-level cities. The results show that market access promoting key core technological innovation. After a series of robustness tests and endogeneity tests， the above conclusion remains valid. Mechanism tests show that market access enhances regional key core technological innovation levels by deepening specialized division of labor and improving resource allocation efficiency. The innovation incentive effect of market access is more significant in northern cities， regions with a lower level of intellectual property protection， and regions with a lower level of digital infrastructure construction. In addition， optimizing product export channels and leveraging the enabling role of fiscal education and science expenditures can help further exert the positive impact of market access on key core technological innovation environmental pollution is not conducive to creating a favorable innovation ecosystem and hinders the incentive effect of market access on key core technological innovation. This paper not only provides a theoretical explanation for strengthening key core technological innovation through market access， but also offers a theoretical basis and practical support for relying on the construction of a unified national market and fully releasing the advantages of an extremely large market scale to enhance innovation efficiency.