With potassium persulfate (KPS) as initiator,graft copolymerization of ethyl acrylate (EA) onto water-soluble hydroxypropyl methylcellulose (HPMC) was investigated in aqueous medium.Effects of monomer concentration,initiator concentration,matrix concentration,and reaction temperature on the percentage of grafting (G) and grafting efficiency (GE) were studied.The results show that G and GE values both increase with the the increase of EA concentration and KPS concentration; when raising HPMC concentration from 0.12 mmol/L to 0.47 mmol/L,G decreases,while GE increases;and when raising reaction temperature from 50 ℃ to 65 ℃,G increases,but GE decreases.In addition,the graft copolymers were characterized by Fourier transform infrared ( FTIR) spectra and transmission electron microscopy (TEM) methods.