In this paper, a novel silica gel affinity sorbent with poly(1-vinylimidazole) (PVI) ligand was prepared for the selective removal of endotoxin (LPS) from a water or a BSA solution. The vinyl silane-modified porous silica gel particle SiO(2)-g-KH570 was used as macromonomer, and PVI was grafted on by heterogeneous graft copolymerization. First, the effect of reaction conditions on the grafted degree (GD) of PVI was investigated in detail by thermogravimetry. Then, the influences of initial LPS concentration, pH and ionic strength of the tested aqueous solutions on LPS removal ability of PVI-g-SiO(2) affinity sorbent were studied and compared with those of His-g-SiO(2) affinity sorbent. The results showed that maximum LPS removal capacity was obtained with a GD about 2.5 wt% and the PVI-g-SiO(2) affinity sorbent had better selective removal of LPS compared to His-g-SiO(2) affinity sorbent in both water and BSA solution. The affinity mechanism between PVI and LPS is also discussed in this paper. All of our results indicate that PVI is a good ligand for LPS removal. (C) 2011 Elsevier Ltd. All rights reserved.