A star polymer composed of three poly(ethylene glycol) (PEG) arms and one poly(N,N‐dimethyl acrylamide) (PDMA) arm (PEG3–PDMA) was synthesized by amidation and atom‐transfer radical polymerization. The structure of PEG3–PDMA was confirmed by 1H‐NMR and gel permeation chromatography results. The surface adsorption and protein‐resistance behaviors of the star polymer PEG3–PDMA, diblock copolymer PEG–PDMA, and homopolymer PEG were investigated by a quartz crystal microbalance with dissipation. The results indicate that the PEG3–PDMA coating could reduce protein adsorption to 13% at least, more effectively than the PEG–PDMA coating; this indicated that the protein‐resistance properties depended on the PEG chain density and surface coverage. If PEG3–PDMA were to be used as the physical coating in capillary zone electrophoresis, it could yield a well‐suppressed eletroosmotic flow with greater stability and separate proteins with a lower relative standard deviration (RSD) of protein migration time and a higher separation efficiency than a bare fused‐silica capillary in a broad pH range. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013