Sodium acrylate was grafted onto cornstarch by microwave irradiation to synthesize a superabsorbent, in which potassium persulfate (PPS) was used as the initiator and polyethyleneglycol diacrylate as the crosslinker. It was found that microwave irradiation could substantially accelerate the synthesis, without the need to remove O-2 or inhibitor. Catalyzed by p-toluene sulfonic acid, polyethyleneglycol was esterified with acrylate to synthesize the crosslinker. An orthogonal test of L-9(3(4)) was designed to study the effects of relevant factors on absorbency and yield of products, including microwave power, irradiation time, initiator amount, and crosslinker content. Microwave power was believed to be the most significant factor affecting the swelling ratio and solubility of the product. Optimized experimental results showed that 10 min of microwave irradiation at 85-90 W could produce a cornstarch-based superabsorbent with a swelling ratio of 520-620 g/g in distilled water and solubility of 8.5-9.5 wt %. (C) 2004 Wiley Periodicals, Inc.