The graft, copolymerization was carried out by methyl acrylate with sage starch in which eerie ammonium nitrate was used as an initiator. It has been found that the rates of graft polymerization and grafting efficiency were dependent upon the concentration of eerie ammonium nitrate (CAN), methyl acrylate (MA), sage starch (AGU, anhydro glucose unit), mineral acid (H2SO4), and as well as reaction temperature and period. A rate equation of polymerization was established from the proposed reaction mechanism, and the rate of polymerization (R-p) was the first-order dependence of the MA monomer concentration and square root of the CAN concentration. A new kinetic model of the grafting reaction has been proposed, and a normal kinetics of methyl acrylate polymerization was observed. An equation of a predicted model relating the graft fraction of poly(methyl acrylate) with the sage starch has been derived, and validity of the predicted model was verified by the experimental results.