Abstract: A super absorbent resin of starch-acrylic acid graft copolymer was synthesized under microwave irradiation using N,N＇-methylene bis-acrylamide as a crosstinking agent. The influences of the selection of starch and initiator, the amount of initiator and crosslinking agent, neutralization degree of acrylic acid（ AA）, ratio of starch to AA, microwave power level and irradiation time on the distilled water absorption amount of resin were investigated. The results indicated that the gelation of starch improved the water absorption ratio of resin largely and the process of gelation decreased the effects of starch species on absorption ratio. Persulphate was proved both cheap and effective as initiator. Using corn starch as material, the maximum absorption amount of resin was 1110g · g^-1 under the optimum conditions of 0.3wt% initiator（ potassium persulphate）, 0.02wt% crosslinking agent, 60% neutralization degree of acrylic acid, the ratio of starch to acrylic acid of 0.25, microwave power level of 231W and 4min. Under microwave irradiation, the synthesis and drying of super absorbent resin could be completed at one step without nitrogen. Compared to conventional heating method, the methods had the striking advantages of short reaction time, simple process and low cost.