Abstract: Promoting the transformation and upgrading of resource-based cities and moving towards a new stage of green growth are the key paths to achieving high-quality development.Based on a quasi-experimental design,empirical tests were conducted on the impact and mechanism of the transformation policy of resource-based cities on green-growth efficiency during 2009-2020.It is found that the transformation policy of resource-based cities has a significant positive impact on green-growth efficiency.However,due to possible reasons such as exit barriers to traditional production capacity,incubation cycles of emerging alternative industries,and low policy implementation efficiency,the impact has a certain time lag,with the policy effect having gradually strengthened since 2016.The results of the mechanism and heterogeneity test show that the transformation policy of resource-based cities can promote the green-growth efficiency by optimizing the industrial structure and alleviating the resource dependence,and the most obvious effect is in declining cities,of which the policy promotes the optimization of industrial structure and adjustment of resource dependence.Further research reveals that from a spatial perspective,both the transformation policy and green-growth efficiency of resource-based cities demonstrate significant spatial spillover effects.To promote the green development of resource-based cities,it is necessary to formulate long-term support policies at the national level to promote sustainable prosperity,necessary to emphasize the synergistic mechanism effect of optimizing industrial structure and adjusting resource dependence and necessary to implement differentiated transformation strategies tailored to different types of resource-based cities.

Key words: resource-based cities, transformation policy, green-growth efficiency, SBM model, DID