The concentrations of total hydrolyzable amino acids(THAAs) were investigated in 8 kinds of typical plants of both East Lake Taihu and Gonghu Bay, in order to find the links and differences of composition of THAAs in the typical plants, sediments and water as well as the composition of THAAs in different typical plants of Lake Taihu. The form and composition of 15 kinds of THAAs in 18 samples were analyzed by o-phthalaldehyde pre-column derivatization-RP-HPLC. The average concentration of THAAs in typical plants of East Lake Taihu was 861.6±182.96μmol/g. The average concentration in typical plants of Gonghu Bay was 700.0±232.3μmol/g. The comparison of the concentrations of THAAs in different kinds of plants showed submerged macrophytes and floating-leaved macrophytes had the highest concentration of THAAs, followed by emerged macrophytes and terrestrial plants. The dominating amino acids were Asparagine, Glutamic acid, Arginine, Alanine and Lysine, which accounted for more than 50% of concentration of THAAs. About 30.7%-94.7% of the N in plants were from THAAs, which was an important source of N in plants. Meanwhile, in comparison with the composition of THAAs in sediments and water in Lake Taihu, the typical plants generally aligned with sediments but different from the water. It showed that THAAs in plant may be an important source of the THAAS in sediments.