3.0 g of chitosan was weighed into a 250 mL four-necked flask, and then poured into 60 mL of isopropanol for 1 hour. 4.4 g of vanillin was dissolved in a mixed solvent of 120 mL of isopropanol and ethanol (V (isopropanol): V (ethanol) = 1:1), and then placed in a chitosan soaking solution, and stirred. The chitosan and vanillin were uniformly dispersed, and a water bath protection device was placed in a four-necked flask, and placed in a microwave oven (XH100B, supplied by Beijing Xiangyu Technology Development Co., Ltd.), and reacted at 300 W at 70 ° C for 12 min. After cooling, suction filtration, soaking the filter residue with 1 mol/L NaOH solution for 5-8 h, then filtering, washing with deionized water and acetone, and drying to obtain a yellow powdery product. The synthetic route of preparing CS-g-VA graft by microwave irradiation is shown in Fig. 1.