Abstract: 【Objective】The riparian vegetated buffer strip can effectively absorb and remove phosphorus from surface runoff, thus significantly reducing the input of phosphorus into lakes. Several riparian vegetated buffer strips were built on a slight slope and their ecological effects were studied to reduce agricultural non-point source pollution and ecologically restore the eutrophic Taihu Lake.【Method】In this study, we examined four poplar buffer strips(20 m × 50 m)of different densities next to Taihu Lake. PVC tubes were laid underground parallel to each other at different depths(20, 40, and 60 cm)in each width in the buffer strips. Three groups of leaching tubes, which were used as collecting devices for surface runoff water, were set in each width as duplicates with three tubes in each group. Water samples were collected after heavy rainfall events during April, June, July and September and samples were preserved at a low temperature for phosphorus content analysis. Concentrations of phosphorus which was removed by poplar buffer strips with different widths and densities in different seasons were analyzed in the runoff water to determine which buffer strips are most suitable.【Result】①Removal rates of dissolved phosphorus(DP)and total phosphorus(TP)in runoff water reached a maximum of 36.91% and 26.50%, respectively, and a maximum removal rate of 63.30% for PO^3-₄ occurred in June. Removal rates of PO^3-₄,DP and TP decreased in April and September compared with that in June and July. Significant differences were observed in PO^3-₄, DP and TP concentrations among months(P<0.05; F=2.382,2.052,2.758; df=180), and phosphorus removal rates were significantly correlated with time(P<0.01; F=3.464,3.265,3.279; df=180). ②There was no significant relationship between the removal rate of pollutants in runoff water and buffer strip density. Buffer strips with low plant densities did not effectively remove pollutants, and buffer strips with high plant densities were not conducive to healthy poplar growth. Thus, there was a threshold of optimum plant density. ③As the widths of buffer strips increased, concentrations of PO^3-₄, DP and TP in runoff water decreased and removal effectiveness increased. The removal rate of PO₄^3- was higher than that of TP, while the removal rate of DP was the lowest. Removal rates of PO^3-₄ and DP in 20 cm deep water were high in each width. The removal rate of TP in 40 cm deep water was higher than that in 20 cm deep water, and the removal rates of PO^3-₄, DP and TP in 60 cm deep water were the lowest. Concentrations of PO^3-₄, DP and TP in different runoff water depths in the anterior 15 m width varied significantly(P<0.05; F=3.232,2.808,2.175; df=180). As width increased, the concentrations of PO^3-₄, DP and TP in runoff water did not change significantly. The effects of the 15 m wide buffer strip was close to that of 50 m wide buffer strip for phosphorus removal so that would effectively remove large amounts of phosphorus from runoff water.【Conclusion】The riparian buffer strip of poplar plantation showed higher phosphorus removal efficiency in runoff water in summer. The removal rate of phosphorus in runoff water was high in medium density popular, while there were no significant differences in phosphorus removal rates between buffer strips with different densities. Results showed that the 15 m wide strip effectively removed large amounts of phosphorus from runoff water. Phosphorus-containing pollutants are only one of the factors contributing to the eutrophication of lake wetlands; thus, the efficiency of removing other pollutants should also be considered. The removal rate of phosphorus is high in the early growing stage, as phosphorus can promote the growth of seedling roots. Long-term studies are needed to examine changes in phosphorus removal efficiencies with the continuous growth and succession of plant communities.