We have synthesized series of superabsorbent polymers (SAPs) by solution free radical polymerization of acrylic acid (AA), acrylamide (AM) with different functional monomers (FM). Three functional monomers including zwitterionic monomer [3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium (MPDSA), cationic monomer (3-acrylamidopropyl) trimethylammonium chloride (APTAC) and anionic monomer 2-acrylamidoglycolic acid monohydrate (AGAM) were selected to provide different charged groups on the superabsorbents. The effect of reaction parameters, such as degree of neutralization, content of initiator and crosslinker on the swelling capacity were assessed. The water absorbency of the superabsorbent were characterized in the distilled water, 0.9 wt % NaCl solution and the mixed solution containing 60 mg L-1 CaCl2 and 30 mg L-1 MgCl2, respectively. In addition, the swelling rate and water retention capacity in the soil were also investigated. Finally, the mechanism of different absorbency induced by the variety kinds of functional monomers was studied by XPS and FTIR, and tentative interpretation was presented as well. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2828-2836, 2009