A straw-reinforced grafted starch composite resin (SSCR) was prepared via grafting and cross-linking co-polymerization with multi-monomers, using raw starch as a matrix and reed straw fine particles as a reinforcing material to the starch matrix. Its structures were characterized by carbon-13 nuclear magnetic resonance, scanning electron microscopy, X-ray diffraction, and the Brunauer–Emmett–Teller technique. The SSCR had enhanced physico-chemical stability due to the formation of a “sea–island” structure, including enhanced resistance to acid/alkali effects and flow abrasion. The introduction of positively charged graft chain segments on SSCR significantly improved its adsorption capacity to active and direct dyes. In the static adsorption experiment, the decolorization rate (DR) of SSCR for the simulated textile printing and dyeing wastewater was up to 85.42%, which had advantage over 201 × 7 ion exchange resin (DR = 38.53%) and activated carbon (DR = 60.19%). In the dynamic adsorption experiment, the SSCR was used as packing material for the column bed. The DR of the SSCR bed for the simulated textile printing and dyeing wastewater was up to 99.95%, and after six dynamic adsorption–regeneration circulations the DR was not lower than 95%.