Herein, we have theoretically investigated the optical properties of the two Au-8 complexes with different shapes of the Au-8 cluster core. From the results of TD-DFT and DFT calculations, it was found that the shape of the Au-8 clusters in the two Au-8 complexes greatly influenced their optical properties, such as absorption and photoluminescence spectra. In particular, the intensities of their photoluminescence spectra are greatly decreased with an increase of the Au-Au bond length variation of the Au core cluster in the S-1 states of the Au-8 complexes.