Microwave radiation could promote the monomer or reaction liquid fast, activate certain groups of macromolecule chain, and have no damage. Compared with the traditional heating method, microwave radiation is able to complete in one step by drying process, simplify technological process, shorten the reaction time, and reduce energy consumption. In this experiment, starch and acrylic acid are used as main raw materials, potassium persulfate is used as initiator, N, N′- methylene diacrylamide is used as crosslinking agent, and high water absorbent resin is prepared by microwave irradiation. The effect of reactive monomer/starch ratio, neutralization degree of acrylic acid, the amount of initiator, and cross-linking agent on the water absorbing properties are studied. The orthogonal experiment results show that the optimal reaction conditions are as follows: The ratio of monomer to starch is 9:1, initiator dosage is 0.4%, crosslinker dosage is 0.08%, and the neutralization degree of acrylic acid is 85% in microwave low-fire heating for 5min. Under such conditions, the water absorbency of the product is 569.95g/g, and getting to saturation in 40min. The effect factors of resin adsorption distillation water ratio from major to minor are monomer/starch>neutralization degree of acrylic acid＞dosage of initiator＞cross-linking agent dosage, the optimal scheme is A₂B₂C₃D₃, the optimum synthetic product is characterized by SEM, the thermal gravimetric test shows the product has the good thermal stability. Microwave radiation method is able to greatly shorten the reaction time, and simplify the process.