This study synthesized cellulose-g-poly(acrylic acid) with high water absorbency using the cellulose extracted from pineapple leaves. The synthesis experiment used a novel combination of ethylene glycol dimethacrylate (EGDMA) and azobisisobutyronitrile (AIBN) as the cross-linker and the initiator, respectively. Experimental results showed that the concentrations of AIBN and EGDMA had significant effects on the structure and the water absorbency of the cross-linked materials. The cellulose-g-poly(acrylic acid) synthesized with 0.5 wt% AIBN and 0.5 wt% EGDMA had an excellent swelling capacity of 1900 g/g in distilled water, significantly larger than previously reported ones. Compared with poly(acrylic acid), the cross-linked product demonstrated an absor-bency improvement of 1.65 times in distilled water and 1.27 times in 8.6 ppm NaCl solution that was the highest salinity level in Ben Tre, Vietnam, in March 2020. Therefore, the obtained product showed high potential for agricultural applications, especially in coastal regions facing a growing thread of saltwater intrusion.