A novel wheat straw composite superabsorbent was prepared by graft polymerization with acrylic acid (AA), acrylamide (AM), and maleic anhydride-modified wheat straw in aqueous solution, using N,N-methylene-bis-acrylamide (MBA) as a cross-linker and ammonium persulfate (APS) and sodium bisulfite (SBS) as redox initiators. Factors influencing the degree of carboxylation, such as reaction time, reaction temperature, and the amount of maleic anhydride, were investigated. Morphologies and structure of the wheat straw composite superabsorbent were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and X-ray diffraction (XRD). Water absorption of wheat straw composite superabsorbent was rapid, requiring 13.1 min to reach 63% of equilibrium absorbency (781 g/g). FTIR spectra indicate that maleic anhydride has been reacted onto the wheat straw backbone and the structure of wheat straw graft copolymer is formed. SEM data show that the fibrous morphology of wheat straw disappears and gel aggregates with many large microporous holes are formed after wheat straw graft modification. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3404-3410, 2013