With the faster urbanization and the higher living environment requirements of people, the urban green area is getting increasingly attention. But green irrigation consumes huge tap water, causes the waste of high-quality water resources. The reclaimed water meets the standard of green irrigation and the source is sufficient, it is a good alternative water source for urban greening. The eco-economic benefit of using reclaimed water as greening water was evaluated in this paper. The composition of benefit was analyzed and the difference in benefit brought by using reclaimed water greening instead of tap water was quantified based on emergy theory. Taking Zhengzhou in 2018 for example, the results showed that the eco-economic benefit of reclaimed water greening was remarkable. The total eco-economic benefit was $4.05 billion, which was three times of that of tap water. Among the benefits, economic benefit accounted for the largest proportion, reaching 69.22%. After deducting the cost, the net eco-economic benefit of reclaimed water greening was $2.00 billion, while tap water was negative. Therefore, using reclaimed water to irrigate urban green area can save a lot of high-quality water and bring a lot of economic, social and ecological environmental benefits. The quantitative results of this paper can provide reference for the promotion of reclaimed water greening and the allocation decision of reclaimed water in water shortage areas. And it is helpful to improve the utilization efficiency of water resources and alleviate the shortage of urban water resources.