In normal conditions, dissolved P, NH_4-N and NO_3-N in the surface waters of rice fields could be diffused within 10 m, and the diffused distance increased in the order of dissolved P 15 m width could decreased significantly the concentrations of N and P in drainage. Therefore, rice fields without application of fertilizers could be used as a riparian buffer to control runoff N and P in rice production area. The mechanism of rice buffer controlling N and P runoff loss was similar to wetland.