The coating material changes the mechanical and optical properties of a single material. Using the Discrete Dipole Approximation (DDA) method, the influence of SiO2shell material, size and morphology on peak value, peak location and near-field distribution of optical absorption spectrum of Au@SiO2 core-shell single crystal octahedron nanorod is systematically studied. The results show that the optical absorption spectrum of Au nanorod coated with SiO2 shell also shows transverse and longitudinal absorption peak. With the increase of SiO2 shell thickness, the intensity of the Au@SiO2 core-shell single crystal octahedron nanorod’s transverse and longitudinal absorption peak decreases significantly, the position of the transverse absorption peak is slightly blue shifted, however the longitudinal absorption peak location is significantly red shifted. The SiO2 shell can improve the hardness of the nanorod and change the peak value and position of optical absorption peak, which weakens the surface plasmon resonance intensity of Au core.