In order to find out the characteristics of colloidal nutrient and phytoplankton under different wind conditions in Lake Taihu, observation were carried out and samples were collected. Colloid was collected by using cross-flow ultrafiltration system. Organic carbon, nitrogen, and phosphorus in colloidal, dissolved and other fractions of water samples were determined, and concentration and biomass of phytoplankton were also determined. The result showed that the concentration of colloidal nitrogen (CN), colloidal phosphorus (CP) increased with the increasing of wind speed when the wind speed was less than 4 m/s, and did not increase or even decreased with the increasing of wind speed when the wind speed was more than 4 m/s. The concentration of Chl-a, phytoplankton, cyanobacteria, and biomass of cyanobacteria increased with the increasing of wind speed when the wind speeds was less than 4 m/s, and decreased with the increasing of wind speeds when the wind speed was more than 4 m/s. It was indicated that the small wind-induced waves are of advantage to the float or growth of cyanobacteria while the big wind-induced waves are of disadvantage to the float or growth of cyanobacteria. Concentration of CN and CP are significantly correlated with concentration of phytoplankton and cyanobacteria, indicating that algae and their production are main sources of CN and CP in summer in Lake Taihu.