The purification effect and mechanism on polluted water by ecological beds systems of Rumex acetosa Linn were studied and the experiment went on 48 days.The results indicated:The removal rate for total nitrogen and NH 4-N was 92.40% and 97.00%,which are 4.47,1.10 times greater than no plant systems,and the remove for NH 4-N depend on nitration of nitrifying bacteria,on the contrary the remove for NH 4-N of the no plant systems depend on ammonia volatilization.The NO-3-N of Rumex acetosa Linn systems is from high to low,however,the no plant systems is no obvious changes.The remove effect for total phosphorus and COD is 79.17%,86.63% in the end experiment,which had a significantly different with no plant systems.The experimental result demonstrates that the Rumex acetosa Linn is recommended as one species of aquatic vegetation in phytoremediation for polluted water.