Abstract:     Green innovation efficiency reduces resource consumption and environmental costs while achieving technological innovation. This approach integrates technological advancements with environmentally friendly practices, which is a crucial strategy for advancing urban economic development. Although trade frictions are known to positively influence environmental regulation within this context, the underlying mechanisms of their impact require further investigation. Based on the Porter Hypothesis and the Profit Quality Analysis Theory, this study employed a panel data set comprising 2085 county-level cities from the China City Statistical Yearbook, spanning from 2004 to 2021. A comprehensive research framework was established, and utilized the mediating effect analysis, difference-in-differences method, and group testing to explore the mechanisms and pathways through which trade frictions influence urban green innovation efficiency. The findings of the study were as follows: (1) Trade frictions positively enhance urban green innovation efficiency; (2) Industrial resilience acts as a partial mediator in the relationship between trade frictions and urban green innovation efficiency, with financing capacity being the most significant, followed by operational and investment capacities; and (3) The influence of trade frictions on urban green innovation efficiency is particularly noticeable in eastern cities, larger cities, digital cities, and cities with lower savings levels in China. Additionally, industrial resilience exhibits a "first-mover advantage" and a "spatial spillover" effect on urban green innovation efficiency. The research findings have not only broadened the scope of studies on the determinants of urban green innovation efficiency but also deepened the understanding of the nature of trade friction and coping strategies and they will provide practical inspiration to enhance the resilience of urban industries and promote the efficiency of urban green innovation.

Key words: trade friction, green innovation efficiency of cities, industrial resilience of cities, Porter Hypothesis, profit-quality analysis