"Sea-island" structure silver/polyaniline (Ag/PANI) nanocomposites were synthesized through sonication of an aqueous solution with silver nitrate and aniline at the temperature of 20 ± 1°C under nitrogen atmosphere. The nanocomposites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy,field emission scanning electron microscopy, and energy dispersive spectrometry, respectively. Furthermore, Ag/PANI nanocomposites were immobilized on the surface of glassy carbon electrode (GCE) and electroactivity behavior was investigated by cyclic voltammetry and differential pulse voltammetry. The obtained sea-island structured Ag/PANI nanocomposite-modified GCE showed high electrocatalytic activity for the oxidation of l-tyrosine.