Foreign trade in subdeveloped regions may lead to serious environmental problems. The direct and possible indirect ways in which foreign trade correlates with green economic efficiency in subdeveloped regions are qualitatively analyzed. Empirical tests are conducted based on the data of 80 prefecture-level cities in Central China. Results show that: (1) Foreign trade in Central China has a significant parabolic type of relationship with green economic efficiency. (2) Foreign trade in Central China will indirectly correlate with green economic efficiency through stimulating industries agglomerated in big cities, changing the level of industrial specialization and adjusting policy and technical environments. Whether the indirect relation between foreign trade and green growth is positive is determined by the scale of foreign trade itself. (3) The relation between foreign trade and green economic efficiency in different cities of Central China is heterogeneous. From the perspective of spatial heterogeneity, the negative relation of cities along major rivers and cities not belonging to capital city groups is more significant. From the perspective of city characteristic heterogeneity, a parabolic type of relationship of foreign trade with green economic efficiency is significant in large cities or cities with a pleasant policy environment, whereas the relationship is negative in small and medium sized cities or cities with a high proportion of manufacturing. Policy implications are proposed.

Improving the pleasantness of the policy environment in Central China stimulates economic growth, but it also contains higher risks of pollution. Based on the data of 80 cities in Central China from 2006 to 2018, the entropy method was used to estimate the pleasantness of policy environment in the region. How the policy environment has changed and whether the pleasant policy environment in the region is conducive to green growth were empirically studied. The results show the following: (1) The current attempts to improve the pleasantness of the policy environment in Central China is not conducive to green growth of the region. (2) Improving the pleasantness of the policy environment has indirect negative impacts on green growth through widening the development gap between prefecture-level cities and provincial capitals, as well as encouraging foreign trade; meanwhile, it also has an indirect positive impact through stimulating industrial diversification. The policy environment does not indirectly affect green growth through affecting technological innovation. (3) The policy environment in Central China will have a heterogeneous effect on the green growth of cities from the perspective of spatial heterogeneity and heterogeneity of city characteristics. In this paper, policy implications are proposed.