Abstract: Au@SiO₂  nanocomposite  was prepared. A novel DNA electrochemical sensor was fabricated by coating Au@SiO₂ nanocomposite on glass carbon electrode and subsequently by immobilizing DNA probe on the modified electrode. The electrochemical behavior of the nanocomposite film was investigated by cyclic voltametry and different pulse voltametry (DPV). The experimental conditions including the immobilized temperature, immobilized time, hybridization temperature, and hybridization time were optimized using ［Fe(CN)₆］^3-/4-solution as probe. Under the optimization condition, the developed biosensor showed a good linear relationship between the current peaks and logarithm of the target DNA concentration in the range of 1.0×10^-13~1.0×10^-10mol/L with a low detection limit of 1.0×10¹⁵mol/L. The developed method has advantages of simplicity, rapidity and sensitivity.