为解决全球面临的水环境污染难题，我国进行了一项重大的制度革新——河长制，面临环境保护与经济发展的两难困境，河长制能否实现经济增长与环境治理的双重红利是我们亟需探讨的问题。将河长制政策实施作为一项准自然实验，基于长江经济带2006~2019年108个城市的面板数据，采用渐进双重差分法实证考察水环境治理政策对经济绿色转型发展的政策效果及其驱动机制。研究结果表明：（1）河长制政策的实施具有明显的污染治理效果，且能够显著推动长江经济带经济绿色转型发展；此外，随着河长制实施强度的增加，其对经济绿色转型的促进效果越强；（2）下游区域河长制促进经济绿色转型的效果更加显著，低污染地区在河长制政策实施后推进经济绿色转型力度更强，且河长制的绿色效应在经济发展高水平城市尤为突出；（3）河长制能够通过激发绿色技术创新以及推动产业结构升级进而促进长江经济带经济绿色转型发展，且官员激励对河长制促进经济绿色转型发展的影响具有重要的调节作用。

For the purpose of solving problem of global water environment pollution, China has been carrying out a major institutional innovation-the River Chief System (RCS). Facing the dilemma of environmental protection and economic development, it is urgent to explore whether the RCS can achieve the double dividend of economic growth and environmental governance.Using the RCS as a quasi-natural experiment, we empirically examined the effects of water environment management policies on the development of economic green transformation and their driving mechanisms,by employing the progressive difference-in-differences method, based on a panel data of 108 prefecture-level cities in the Yangtze River Economic Belt from 2006 to 2019. The results showed:(1) The implementation of the RCS had a significant effect on pollution control and could significantly promote the economic green transformation of the Yangtze River Economic Belt. In addition, with the strengthened implementation of the RCS, a stronger effect had been indicated on the promotion of the green economic transformation.(2) The effect of the RCS in the downstream region was more significant in promoting the economic green transformation. Stronger efforts were shown in the low pollution areas, and the green effects of the RCS were especially prominent in the cities with high level of economic development. (3) The RCS could promote the economic green transformation development by stimulating green technology innovation and promoting industrial structure upgrading. The official incentive played an important role in moderating the effects of the RCS in promoting the economic green transformation development.