Four aminogenized nanoparticles were prepared as follows: γ-Fe₂O₃@SiO₂-cysteamine, γ-Fe₂O₃@SiO₂-APTMS, γ-Fe₂O₃@SiO₂-PEI, γ-Fe₂O₃@SiO₂-G1.0. Magnetic solid phase extraction experiments of L-phenylalanine have been carried out at a concentration of 2.5×10^-6 mol/L, different extraction times and pH gradients. The lower fluorescence intensity of supernatant indicated the better extract effects. As for γ-Fe₂O₃@SiO₂-G1.0 nanoparticles, the best adsorption was obtained at pH=5, while the adsorption time was 8 h. As for γ-Fe₂O₃@SiO₂-PEI nanoparticles, less adsorption than above could be obtained at pH=3 and 0.5 h. γ-Fe₂O₃@SiO₂-PEI nanoparticles took less time to extract L-phenylalanine. Functionalized γ-Fe₂O₃ nanoparticles are promising for solid-phase extraction of L-phenylalanine.