Eichhornia crassipes (water hyacinth) was cultivated under different iron (Fe), manganese (Mn) and silicon (Si) nutrient treatments for its biomass characteristics research which was determined by various items including nutrient element content (Fe, Mn and Si), adsorption sites and active function groups. The results show that Mn and Si can enhance acidic sites of the plant, in which Mn plays a great role, but Fe reduces the acidic sites. The sequence of acidic sites' amount among three parts of the plant is root > stem > leaf, in the treatment of Fe, Mn and their combination, and leaf > stem > root in Si treatment. The amount of alkaline sites is less than that of acidic sites, and the difference in their distributions among three parts of the plant is not great. Mn and Si treated Eichhornia crassipes stalks have more amorphous material, such as lignin, pectin and xylan (hemicellulose), which have more functional groups of -OH, -COOH and acidic sites.