Abstract: 【Objective】Taking the farmland drainage ditches in the polder area of Chaohu Lake as the research object, the output characteristics and temporal and spatial distribution of nitrogen and phosphorus in the farmland drainage ditches in the polder area was explored.【Method】From 2015 to 2016, different sections of farmland drainage ditches in the polder area of Chaohu Lake were sampled and monitored, and the nitrogen and phosphorus contents of water in the ditches were determined. 【Result】 The results showed that the average concentrations of NH4 +-N and NO3 --N of water in the drainage ditches were 1.1 mg/L and 1.3 mg/L, respectively, which were above the class III water quality standard. The TN concentration was 1.6-11.6 mg/L, the TP concentration was 0.1-1.0 mg/L, and the average concentrations of TN and TP exceeded the class Ⅴ and Ⅳ water quality standards, respectively. The nitrogen and phosphorus concentrations in farmland ditches water change with season obviously. The concentrations of TP and NH4 +-N were lower in summer and autumn, and the concentrations of TN and NO3 --N were higher in spring and summer and lower in autumn and winter.【Conclusion】The farmland drainage ditch has the function of intercepting and purifying nitrogen and phosphorus. The nitrogen and phosphorus concentrations in the ditches of vegetable-rice area were highest, followed by those in ditches of rice-wheat-residential area and ditches of rice-wheat cultivation area. The concentrations of nitrogen and phosphorus in the drainage ditches of the polder area were slightly lower than those of the farmland ditches, but higher than those of the Jiyu River.