Abstract: In order to research the removal effect on non-point source pollutant of ecological ditch, in the summer and winter of 2013, water samples in different types of ditches of Caohai wetland were collected and analyzed, using comprehensive water quality identification index method to evaluate water pollution in sewage ditches, artificial ecological ditches and farmland ditches. The results indicated that the content of TN in spring was less than that in summer, the content of TP in spring was higher than that in summer, TN was the main pollution factor, the water quality was the worst in the water district area. Compared project ditches with farmland ditches, removal rate increased 20-30 percentage points, which reached class域. It showed that ecological ditches was a very effective way to control non-point source pollution of farmland and to protect water quality of Caohai wetland.