Understanding the optical properties of nanometer-scale noble metals is important for the nanoplasmonic devices. The bulk gold and thin film are calculated by density functional theory (DFT) with LDA, PBE, and GLLBSC functionals, respectively. The GLLBSC results for bulk gold are closer to the experimental data because the GLLBSC functional has better descriptions of transition energy. The Im(ε) of thin film calculated by LDA and PBE are overestimated. The effects of DFT-based optical properties are performed by conducting electromagnetic simulations. The transmission for the gold thin film by GLLBSC is blue-shifted. The gold grating structure with the GLLBSC-based optical permittivity has strong localized streamlines of Poynting vector in the corner edges at the resonance condition.