The invention relates to a method for preparing heavy metal ion adsorption materials of crop straws. The method is characterized by comprising the following processing steps: adding straw powder into N, N-dimethyl formamide; putting the straw powder and the N, N-dimethyl formamide into an ultrasonic rinsing tank for ultrasonic cleaning at a certain temperature for a certain time; then adding phytic acid and urea into the above system, heating to 50-90 DEG C, cooling products to a room temperature after reaction for a certain time, and then precipitating, washing, drying and grinding the products to obtain phytic acid modified straws; neutralizing itaconic acid with NaOH, then adding the phytic acid modified straws, acrylamide, vinyl pyrrolidone and cross-linking agents, after the mixture is fully stirred, gradually heating to 40-60 DEG C, and finally slowly and dropwise adding redox initiators into the polymerization system to initiate a polymerization reaction that lasts for 3-5 hours; after the polymerization is completed, performing precipitation, washing and drying to obtain the heavy metal ion adsorption materials of crop straws. The adsorption capacity reaches 50-800mg / g for heavy metal ion water solutions of which the initial concentration is 100-1000mg / l, and adsorption equilibrium is reached after adsorption at the room temperature for 50-150 min.