Magnetite Fe₃O₄ nanoparticles (NPs) were prepared by chemical coprecipitation method. Silica-coated magnetite NPs were prepared by sol-gel reaction, subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction, and then were activated with 2,4,6-trichloro-1,3,5-triazine (TCT) and covalently immobilized with bovine serum albumin (BSA). The size and structure of the particles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and dynamic light scattering (DLS) techniques. The immobilization was confirmed by Fourier transform infrared spectroscopy (FT-IR). XRD analysis showed that the binding process has not done any phase change to Fe₃O₄. The immobilization time for this process was 4 h and the amount of immobilized BSA for the initial value of 1.05 mg BSA was about 120 mg/gr nanoparticles. Also, the influences of three different buffer solutions and ionic strength on covalent immobilization were evaluated.