Using the panel data of 274 cities in China from 2003 to 2022, this paper takes the establishment of national-level industrial transfer demonstration zones as a quasi-natural experiment, and uses a multi-period difference-in-difference model to identify the impact of these policies on regional development disparities. The results show that the construction of national-level industrial transfer demonstration zones can significantly narrow the regional development gap. The policy effects are more pronounced in small and medium-sized cities, non-resource cities, cities within the five major urban agglomerations, and non-revolutionary old base cities. The mechanism tests have shown that the construction of these demonstration zones mainly reduces the regional development gap through the effects of technological progress, synergistic industrial agglomeration and employment. Accordingly, local governments should actively promote the construction of national-level industrial transfer demonstration zones, and at the same time explore differentiated institutional innovations based on local advantages and characteristics, and fully leverage the synergistic effects of these policies to further narrow the regional development gap.