At present, under the condition that the water resource is deficient day by day and the worsen trend of water environment is becoming severe increasingly, as well as the advanced and super advanced treatment and the reuse of waste water have been practicable, drainage system should not only be the basic facilities for draining rain and sewage and protecting city environment and water quality of pubic water basin, but also be sublimated to the lifeline project of human society that maintains healthy water cycling and good water environment and realizes sustainable utilzation of water resource. As a valuable drinking water resource, sewage has attracted more and more attention. The article elaborates on the author´s new ideas and concepts about the function, programming and design of drainage system.