运用考虑非期望产出的SBM模型,在测度长江经济带沿线102个城市2004-2018年绿色创新效率的基础上,构建中介效应模型实证分析外商直接投资在环境规制对绿色创新效率影响的中介效应,并基于门槛回归模型,综合考察环境规制在不同FDI发展水平下对长江经济带沿线城市绿色创新效率的影响机制。研究结果表明：(1)研究期内,长江经济带102个城市的绿色创新效率存在较大的空间非均衡性,长江上游和长江中游的绿色创新效率基本保持稳定,长江下游的平均绿色创新效率呈现出不断上升的趋势。(2)加强环境规制,对于绿色创新效率具有显著促进作用,外商直接投资在环境规制对城市绿色创新效率的影响中具有部分中介作用,政府加强环境规制可以在一定程度上有效限制污染型行业外商直接投资的流入,从而促进长江经济带沿线城市进一步提升城市绿色创新效率。(3)在不同FDI发展区间内,环境规制对长江经济带沿线城市绿色创新效率的影响方向并不相同,存在双门槛效应,跨过第一门槛值8.293后,环境规制对城市绿色创新效率由促进作用变为抑制作用,跨过第二门槛值11.695后,环境规制对城市绿色创新效率又再次变为促进作用。

Using the SBM model that considers undesired output, based on measuring the green innovation efficiency of 102 cities along the Yangtze River Economic Belt from 2004 to 2018. An empirical analysis of the relationship among environmental regulation, foreign direct investment and green innovation efficiency in cities along the Yangtze river economic belt is made by constructing a mediation effect model. Based on the threshold regression model, comprehensively examines the impact of environmental regulations on the green innovation efficiency of cities along the Yangtze River Economic Belt at different levels of FDI development. The research results show that: (1) The green innovation efficiency of 102 cities in the Yangtze river economic belt has a large spatial imbalance. The average green innovation efficiency of the upper reaches of the Yangtze river and the middle reaches of the Yangtze river is basically stable, while the average green innovation efficiency of the lower reaches of the Yangtze river shows a rising trend. (2) increasing the intensity of environmental regulation can significantly improve the overall green innovation efficiency of cities along the Yangtze river economic belt, and foreign direct investment plays a significant part of the intermediary role in the relationship between environmental regulation and urban green innovation efficiency. The government"s strengthening of environmental regulations can effectively limit the inflow of foreign direct investment in polluting industries to a certain extent, thus helping cities along the Yangtze river economic belt to further improve the efficiency of urban green innovation. (3) In different FDI development intervals, environmental regulation has different impact directions on the green innovation efficiency of cities along the Yangtze River Economic Belt. There is a double threshold effect. After crossing the first threshold of 8.293, environmental regulation affects urban green innovation efficiency from the promotion effect has become a suppression effect. After crossing the second threshold of 11.695, environmental regulation has once again become a promotion effect on urban green innovation efficiency.

国家自然科学基金项目（面上项目，重点项目，重大项目）