Propagation properties of symmetric surface plasmon polariton (SPP) mode excited through a dipole embedded in Al2O3 layer in Au/Al2O3/Au waveguide have been investigated. The skin effect of symmetric SPP mode vertical to Al2O3/Au interface is presented. The skin depths in the Au layer and in the intermediate Al2O3 layer are 12 and 24 nm, respectively. Moreover, the propagation properties of symmetric SPP mode along Al2O3/Au interface are also analyzed. The propagation lengths of electric and magnetic field component are 0.4 and 0.8 μm, respectively. It is expected that this study will provide additional understanding to the coupling between SPP sources and plasmonic waveguides.