Abstract: Based on the analysis of the structure characteristics and definition of the riparian buffer strip,the primary mechanism to control the rural non-point pollution is discussed from the following aspects:(1) reducing the speed of surface runoff,filtrating and barring the particulate contamination; (2) assimilating dissoluble contamination by vegetable and soil; and (3) facilitating denitrification.Research progress in the fitting width of the riparian buffer strip is discussed,and a view is put forward that the study on the fitting width of the riparian buffer strip only from the point of environment is far from enough in China and the integrated study is necessary for the fitting width of the riparian buffer strip from the point of environment,economy,society,etc.In the end,the future progress in purification mechanism of the riparian buffer strip is prospected.