To examine the pollutant removal efficiency of different sward buffers to runoff and the correlation with biomass, 5 native grasses were selected to construct buffer strips and conduct an experiment under the simulation of agricultural non-point pollution and rainfall characteristics in Shanghai. The results showed: 1) the clarification efficiency to runoff of sward buffers was significantly better than the blank control, the SS average retention rate of Cynodon dactylon buffer strip was the highest, up to 74%;2) the TN and TP average removal rate of Trifolium repens buffer strip was the highest, up to 28% and 25%;3) the clarification efficiency of Lolium perenne buffer was the lowest because of the high temperature;4) the aboveground biomass of C. dactylon was 6.14kg/m², and T. repens was 6.49kg/m², higher than the other species;5) the growth rate of C. dactylon was the fastest, whose biomass in September was almost as six times higher as in May;6) the clarification efficiency of the sward was increased with higher biomass, there was a significant linear correlation between sward biomass and SS removal efficiency.