With the increasing demand of using cellulose more effectively, modification of cellulose by graft polymerization provides a significant route to combine the advantages of natural and synthetic macromolecules for a wide range of potential applications. Synthesis of cellulose-graft-PHEMA copolymer via homogeneous atom transfer radical polymerization (ATRP) in the ionic liquid was researched in this article. FTIR, 1H NMR and GPC were carried out to analyze the effects of different solvents on the polymerization conditions, grafting efficiency, molecular weight distribution, thermal stability and the changes in shape in different solvents of the copolymer as well. The results indicated that the grafting efficiency increased with the increase of reaction time. The obtained graft copolymer cellulose-graft-PHEMA showed good thermal stability, and the copolymer could aggregate into spherical particles with 50nm diameter in DMF and 100nm diameter in the selective solvent butanone.