With the transformation of China’s economy from high-speed growth to high-quality development, the focus of local governments has shifted from pursuing GDP growth to enhancing economic quality and efficiency. Given that the administrative division adjustments between county and district serve as a critical tool for coordinating urban-rural planning and construction, how such adjustments align with this reform trend has naturally become a focus for the governments, academia, as well as broader society.

This paper adopts a dual perspective of growth effect and quality effect to systematically evaluate the policy impact of China’s administrative division adjustments between county and district both on regional economic growth and high-quality development in China based on the city-level panel data from 2007 to 2022 and the dual machine learning method. Then, it further gets the feasible strategy for enhancing the quality effect of the adjustments through the simulation of policy combination, thus providing quantitative evidence for future policy optimization.

The conclusions are as follows: First, the administrative division adjustments between county and district in China shows an obvious characteristic of policy effect transformation. The growth effect was dominated before 2015, while the quality effect gradually appeared after then. Additionally, the quality effect varies across cities depending on the development level, industrial structure, population size, and administrative governance modes. Second, the adjustments are now under the transition stage, during which the quality effect has not yet fully manifested, mainly concentrating on the dimensions of innovation, openness, and sharing. Third, the coordination between urban agglomeration policy and urban “high-speed railway opening” can activate the quality effect of the adjustments effectively, which is a useful attempt to optimize the effect of the reform in future.

Currently, China’s administrative division adjustments between county and district are in a calm-down period. During this period, it is of great necessity to thoroughly summarize both the successful experience and shortcomings of past reforms. This work will ensure that the next round of adjustments can be implemented with targeted planning, better policy application, and systematic feedback, finally facilitating a smooth transition in the policy effect and fully supporting high-quality economic development.