Rainwater comprehensive utilization, as an important aspect of water resources management in low-carbon eco-city, contributes to the solution of these issues such as run-off pollution, river flood arising from urban development, and so on. Based on survey, this paper analyzed the status of rainwater management for domestic green buildings and the rainwater management measures adopted in the low-carbon eco-cities. This paper focused on the analysis of impact of rainwater measures on site runoff coefficient which is set as a synthetic parameter for the evaluation of the storm water runoff situation in the eco-city. According to the average annual rainfall, our country was divided into several regions. The rainwater measures and site runoff coefficients suitable for low-carbon eco-city in different regions were calculated and verified.