In recent years, there has been an increasing awareness of the importance of aquatic micro ecosystem on water and sediment environment. Microorganism secrete biofilm on the sediment, forming new bioflocculation sediment and acting an significant impact on sediment properties and its environmental effects, which is important for the study on the interaction mechanism of various factors in water and sediment environment. In this paper, sediment particles are used as carriers to culture biofilm, and the change of the rheological properties and the adsorption rules on phosphorus element due to biofilm growth were investigated. The effect of biofilm on rheological property of sediment is first studied by the rheological experiment. It is found that the rheological property of biofilm sediment are obviously different from that of original sediment, which shows the characteristics of plastic body with thixotropy. Meanwhile, phosphorus compound KH₂PO₄ is taken as adsorbent to study the influence of biofilm on phosphorus adsorption rules of sediment particles through the isothermal equilibrium adsorption experiment. The results show that the phosphorus adsorption capacity of sediment particles increases with the growth of biofilm.