Abstract: The eutrophic water body with organic nitrogen(ORN) being the main component of nitrogen was studied.The batch cultivation method was adopted to comparatively investigate the transform and removal of nitrogen components in two floating-plant systems(including hyacinth and duckweed systems),foamy board system and control system,at a low water temperature of 6.8～7.2 ℃.The effect of initial COD_Cr levels(27～148 mg/L) at a water temperature of 9.5～13.1 ℃ was also discussed.Results indicated: in the two floating-plant systems,ORN removal rate was 83% and 63% respectively,while total nitrogen(TN) removal rate was 50% and 59% respectively,which were higher than that in the foamy board system(ORN: 39%,TN: 39%) and the control system(ORN: 48%,TN: 43%).COD_Cr removal rate in the two plant systems was 75% and 54% respectively,almost the same as that in the control system(63%) but higher than that of foamy board system(38%).With the increase of initial COD_Cr level,followed by the decrease of DO,in hyacinth system ORN removal rate decreased from 85% to 66% while TN removal rate increased from 19% to 45%.