Grafting sodium polyacrylate onto hydroxyethyl cellulose (HEC-g-PAA) has been carried out by using microwave method. The effect of the reaction conditions such as the concentration of initiator, the neutralization degree of the acrylic acid and the amount of monomer on the percentage of grafting and absorbency have been studied. The swelling behavior of HEC-g-PAA which have different sizes were discussed. The results were analyzed in terms of the non-Fickian equation; the result showed that relaxation contribution is the main cause in absorbing process.