In May 2019，the Political Bureau of the Central Committee of the Communist Party of China approved the “Outline of Regional Integration Development Plan for the Yangtze River Delta”，in which a Demonstration Area of Regional Integration on Ecological and Green Development for the Yangtze River Delta has been brought forward（hereinafter referred as the “Demonstration Area”），aiming at building a pilot showcase on ecologically friendly development，to promote high-quality economic development on the basis of higher ecological protection standards. At the same time，great importance will also be attached on making breakthroughs on cross-boundary cooperation，which will try to achieve more effective regional cooperation and integration while keeping the administrative boundary between different provinces and cities untouched. Comparing with the development targets listed in the Outline of Regional Integration Development Plan，the Demonstration Area still faces a few ecological and environmental protection challenges，eg. pressures on meeting environmental quality standards，alleviation of environmental risks，improvement on ecosystem service functions etc. When looking at the reasons causing these disadvantages or challenges，it’s rather clear that administrative and institutional barriers，as well as policy constrains have played certain roles. This article will discuss the above issues on the basis of reviewing current status of the ecological and environmental protection in the Demonstration Area，as well as cross-boundary cooperation，and explore feasible policy applications，to contribute to the promotion of building Yangtze River Delta city clusters into a new highland of reform and opening，innovative economy，ecological value，and high-quality human settlements.