Abstract: Hydroxyapatite (HAP) nanoparticles were surface grafted with poly(methyl methacrylate) (PMMA) through atom transfer radical polymerization (ATRP). As the amount of grafted PMMA increased, the dispersibility of surfacegrafted HAP (gHAP) in aqueous solution was improved. Bovine serum albumin (BSA) and lysozyme (LSZ) were selected as models to study their adsorption behaviors on HAP and gHAP. Our results showed that the adsorption capacity on gHAP was higher than that on HAP, indicating that the adsorptive property of HAP was improved due to surface modification of HAP with PMMA.