Using bacteria - algal symbiosis characteristics of biological slow filtration system and the effective removal of nitrogen and phosphorus in reuse water for landscape replenishment can effectively prevent the problems of eutrophication of landscape water body result from the high nutrient concentration of nitrogen and phosphorus in water.The experimental of reclaimed water purification by biological slow filter system showed that when biological slow filter system keep the conditions of overlying water depth of 80cm, filter layer thickness of 80cm, filtration rate of 0.1m/h,the average removal rate of total nitrogen, ammonia nitrogen, nitrate nitrogen and potassium permanganate index in water is 57.55%, 50.16%, 46.37%, 66.32% and 47.04% respectively,the removal rate of chlorophyll a is up to 95.75%. After the reuse water is treated by biological slow filter system,the growth of algae is slow and the content of chlorophyll a maintains at a low level during the process of landscape storage,and the content of nitrogen and phosphorus is low and stabilizing.The reclaimed water which is treated by biological slow filter system can be used as the replenishment source of landscape water so as to reduce the frequency of eutrophication.