A group of proteins could interact with nanoparticles to form the protein corona on the surface when introduced into biological system,which would critically impact the biological identity of nanomaterials.[1-3] Elaborate investigation on the components of protein corona on nanoparticles would facilitate the fundamental understanding of the formation and importantly the biological effects of nanoparticles in biological systems.[4] A tryptic nanorazor by immobilizing trypsin on a magnetic Fe3O4 nanoparticle was fabricated to achieve the identification and quantification of the constituents of protein corona on Fe3O4 nanoparticles with significantly high efficiency and obviously reduced self-digestion.Moreover,the identification and quantification of the human plasma protein corona bound on different sizes of Fe3O4 nanoparticles was determined efficiently by the application of magnetic tryptic nanorazor.It was demonstrated that particle size is one of the critical factors which influences the formation of human plasma protein corona on Fe3O4 nanoparticles and the different binding profiles of human plasma proteins on Fe3O4 nanoparticles in different sizes pose great impacts on the bio-distribution and fates of them when they enter into biological system.