Abstract: Wetland,located in the terrestrial-aquatic transverse one,is an important landscape and ecosystem.It is unique combination of the structural and functional attributes that sets wetlands apart from the terrestrial and aquatic ecosystems in their ability to remove or sequester the nutrients and the toxic environmental contaminants.Wetlands have strong functions in maintaining the ecological balance and the water environment stability in watersheds.The watershced wetlands is regarded as a whole to study purification functioning.Fnrstly,this paper makes a detail introduction to purification functioning of wetlands, including their unique attributes that contribute to removal contaminant of the treatment of the wetland components and the progress in the wetland contaminant removal.Secondly,the water quality functioning of wetlands in watersheds is the importance part of this paper.In watersheds,it consists of the local and regional-scale environmental factors that have considerable influence on wetlands functioning,the wetlands functioning categorization and wetlands as a entirety to control non-point source pollution.This paper makes a summary of the watershed wetlands purification functions in particular.Finally some problems concerned are discussed and its future study is also prospected.