Hydroxyethylcellulose-g-methoxypoly (ethylene glycol) (HEC-g-PEG) graft copolymers were synthesized through the etherification reaction between the hydroxyl group of hydroxyethylcellulose (HEC) and iodinated methoxypoly (ethylene glycol) (PEG-I), which was prepared on the basis of two-step reaction. Fourier transforms infrared spectrum (FTIR), nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and iodide oxidation method were used to prove the success of synthesis of graft copolymer. Furthermore, the comparative studies of electro-osmotic flow (EOF) and protein separation in bare-fused silica, HEC and HEC-g-PEG-coated capillary were performed in capillary electrophoresis (CE). The results showed that HEC-g-PEG-coated capillary presented efficient EOF suppression ability and excellent resisting protein adsorption ability. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013