To identify the composition and properties of extracellular polymeric substances (EPS) in aerobic granular sludge (AGS), activated sludge from aerobic tank of a wastewater treatment plant was used as seed sludge in this study. AGS-LAB and AGS-WWTP were cultured from laboratory synthetic wastewater and wastewater treatment plant influent respectively, and the EPS in the two types of AGSs was compared and analyzed. Results showed that the EPS content increased from 84.36 mg/g MLVSS of seed sludge to 122.49 mg/g MLVSS of AGS-LAB and 128.23 mg/g MLVSS of AGS-WWTP, and the protein content in TB-EPS greatly increased while the polysaccharide content slightly changed. The contents of aromatic amino acids, tyrosine/ tryptophan proteins, and aspartic acid proteins in the AGSs were remarkably higher than those in seed sludge. The hydrophilic amino acids contents in three kinds of sludge were relatively lower, while the hydrophobic amino acids presented higher contents. In addition, the total amount of the amino acids in AGSs increased by 28.31% on average. Moreover, the carrier substance hexamethyl-cyclooctasiloxane and ethylene benzene with crosslinking role only existed in the EPS of two AGSs, indicating that they played potential roles in shortening the granulation process of seed sludge and improving the structural stability of AGS.