Method for utilizing rain water on plain roof and device thereof

The method for utilizing flat roof rainwater includes a water-receiving water-storing, drainage and greening system formed from separating channels filled up with soil, a water-receiving and drainagesystem formed from communicating structure connecting these separating channels to make the rainwater flow between them and arch rings and a ventilating radiation channel system formed from space under the arch rings. It is characterized by that two side vertical walls of the separating channel are equipped with bolt through-holes, two ends of rear arch ring are equipped with arched joint grooves, and its two sides possess vertical tile curtain respectively, and the front end of side arch ring has arched joint flange, and its rear end has arched joint groove, and its two sides respectively are equipped with vertical tile curtain with holes, and four sides of shell arch ring respectively possess curved tile curtain.