Gigaporous PS microspheres, prepared in a previous study, were hydrophilized with modified agarose (Agap-PS), and then a thermoresponsive gigaporous bioseparation medium (Agap-PS-PNIPAM) was prepared through a two-step reaction. Bromoacetyl groups were coupled on Agap-PS through acylation to obtain a solid atom transfer radical polymerization (ATRP) initiator (Agap-PS-Br), and poly(N-isopropylacrylamide) (PNIPAM) brushes were grafted onto Agap-PS-Br via ATRP afterwards. The effects of ligands, catalysts, solvent and temperature on NIPAM solution ATRP were investigated in detail, and the amount of PNIPAM grafted on Agap-PS-Br reached to 15. 07 mg/m(2) under optimal conditions. Agap-PS-PNIPAM was characterized by Fourier transform infrared (FTIR) spectra, scanning electron microscope (SEM), mercury porosimetry measurements, laser confocal scanning microscope (LCSM), and protein adsorption experiments. Results showed that thermoresponsive PNIPAM brushes were successfully grafted on the PS microspheres and that the Agap-PS-PNIPAM had good thermo-responsibility. Meanwhile, the gigaporous structure of PS microspheres was well maintained. After modification, nonspecific adsorption of proteins on PS microspheres was greatly reduced. The adsorption amount of bovine serum albumin (BSA) on Agap-PS-PNIPAM at 40 degrees C was 2. 69 times to that at 25 degrees C due to the phase transition of PNIPAM brushes from hydrophilicity to hydrophobicity. Flow experiments showed that the Agap-PS-PNIPAM column had low backpressure, good permeability and mechanical stability. Similarity, the bed permeability (K) of Agap-PS-PNIPAM column at 40 degrees C increased by 15. 7% than that at 25 degrees C owing to the shrinking of PNIPAM brushes. All results indicate that Agap-PS-PNIPAM has great potentials in green high-speed protein chromatography.