Green roof based on green building

The invention discloses a green roof based on a green building. The green roof comprises a mounting base, an assembly groove is formed in the side wall of the mounting base, a top cover plate is assembled in the assembly groove, a fixing frame is fixedly mounted on the side wall of the top cover plate, a rainwater drainage groove is formed in the side wall of the fixing frame, a green plant planting groove is formed in the top of the fixing frame, and a rainwater collecting groove communicating with the rainwater drainage groove is formed in an inner cavity of the fixing frame. Collected rainwater provides water for green plants planted in the green plant planting groove through cooperation of a main water absorption cotton thread and an auxiliary water absorption cotton thread, it is guaranteed that the rainwater is reasonably utilized, the collected rainwater is filtered by arranging a filtering groove and a filtering frame, sundries such as fallen leaves are prevented from entering the rainwater collecting