Abstract: As an important driving force for the transformation and upgrading of manufacturing industry, producer services have become an important engine to promote the high-quality development of China's economy. This paper selects the panel data of 278 cities in China from 2005 to 2018 to empirically test the specific path of producer services agglomeration to improve the efficiency of urban green economy. It is found that: (1) producer services agglomeration can significantly promote the efficiency of urban green economy, and there is a spatial spillover effect. Producer services agglomeration is not only conducive to the improvement of green economic efficiency of the city itself, but also has a positive effect on adjacent cities through spatial spillover, but the spatial effect is less than the direct effect. However, the continuous agglomeration of producer services in cities may siphon off neighboring cities, resulting in negative spatial spillover effect, which is not conducive to the improvement of green economic efficiency. (2) Producer services agglomeration can affect the efficiency of urban green economy through three paths: industrial productivity, knowledge stock and market environment, but there is heterogeneity. Producer service agglomeration has significant direct effect and spatial spillover effect on the improvement of industrial productivity, that is, producer service agglomeration will not only improve the industrial productivity of the city itself, but also drive the industrial productivity of adjacent cities through spatial spillover. Producer services agglomeration can also play a positive role in urban green economic efficiency by affecting industrial productivity, that is, industrial productivity plays a positive intermediary effect. Producer services agglomeration is conducive to the increase of urban knowledge stock and the improvement of market environment, and there is a positive spatial spillover effect. That is, producer services agglomeration is conducive to the increase of knowledge stock and the improvement of market environment in adjacent cities. However, considering the intermediary effect, these two channels do not play a promoting role. The reason may be that the role of these two channels in the process of producer service agglomeration affecting urban green economic efficiency may have nonlinear characteristics. (3) There is a double threshold between the two intermediary effects of knowledge stock and market environment, and they show the ladder characteristics of “from inhibition to promotion, from weak to enhancement” in regulating the agglomeration of producer services and the efficiency of green economy. Only when the knowledge stock and market environment cross a certain threshold, the positive promotion effect of the two action paths will appear. The reason is that only when the urban human capital level is high and the market environment is relatively perfect, it is more conducive to the positive externalities brought by the agglomeration of producer services, which will eventually have a positive impact on the efficiency of urban green economy by accelerating R&D innovation and improving market competition. This study not only examines the specific impact path of producer service agglomeration on urban green economic efficiency, but also confirms the existence of threshold effect and spatial effect, which provides a theoretical basis and policy enlightenment for cities to formulate differentiated producer service agglomeration policies and promote the improvement of green economic efficiency.