Nutrient loss from farmland has become one of the main sources of agricultural non-point source pollution，andit was of great significant to study the interception effect of ecological ditches onnitrogen(N)andphosphorus(P)infarmland drainage under natural rainfall and drainageconditions.Taking ecological ditches flowing into Mauri Lake area asthe research object，the change rule and reducing rate of N and P after interception by multi -stage plant assemblage weresystematically studied for two consecutiveyears.Results showed that the ecological ditch can effectively intercept the nitrogenand phosphorus in farmland drainage in smallwatershed.In 2016 and2017，the average reducing rate of total nitrogen inthe channel is 58.49% and47.61%，respectively.The average reducing rate of ammonium nitrogen is 77.29% and69.72%，respectively.The average reducing rate of nitrate nitrogen is 58.77% and47.79%，respectively.The average reducing rateof total phosphorus is 67.07% and54.47%，respectively.It is generally believed that the ecological ditches can effectivelyintercept and absorb N and P from farmland drainagewater，and can reduce the pollution load of the receiving water body inthe surroundingenvironment.