Rice straw is an agricultural waste which usually appears in a huge amount. Rice straw can be used as a base for the manufacture of superabsorbent polymer which has been developed. Nowadays rice straw can be used as a soil conditioner to function as an absorbent and a storage for groundwater, and can improve the physical properties of the soil to increase productivity in the agricultural sector. This study calculated cellulose content of rice straw in the manufacture of SAP and grafting factors to characteristing the SAP, it also determined functional group from SAP using FT-IR. The method used in the manufacture of SAP are: cellulose extraction, cellulose content test, SAP manufacture, SAP purification, SAP test of functional groups with FT-IR spectrophotometry, and grafting factors test. SAP is made by using a machine with the dose of electron beam radiation of 50kGy. Result  showed that 3460.10 cm-1  functional group is the N-H group absorption band, number 2359.93 cm-1  is O-H absorption band, number 1643.85 cm-1  is C-N absorption band, and number 1384.45 cm-1  is N-O absorption band. Celullose content of rice straw is 49% and the grafting fraction 38%. 
Key words: Rice straw, superabsorben polymer, cellulose, electron beam machine, FT-IR spektrophotometer,