Various adsorbents have been investigated for removing endotoxin from protein solutions. It is believed that electrostatic interaction and hydrophobic intermolecular interaction are the main interactions in adsorption of endotoxin. In this work, a series of novel molecular recognition adsorbents for removal of endotoxin with dimethylamine ligand were prepared by coupling ligands on polymethyl methacrylate. We found that its adsorption capacity of endotoxin increased almost 8 times in the presence of a hydroxyl group at beta-site of ligand. The computer simulation showed that the hydroxyl group at beta-site could form H bond with endotoxin, as a result an octatomic ring was formed. The spacer in adsorbent and the long alkyl chain in endotoxin were located at the same side of the octatomic ring. In this situation, electrostatic interaction, H bond, cooperative effect of octatomic ring and hydrophobic intermolecular interaction effected simultaneously. The combination of endotoxin with adsorbent was tight and adsorption capacity was effectually increased.