We present a comprehensive study on the optical properties of gold-doped rhenium disulphide (ReS2:Au) layer crystal. Its anisotropic optical properties were studied by using the polarization-dependent optical absorption and photoconductivity (PC) measurements. Absorption measurements indicate that the absorption edge shifted toward high energy as the sample was slimmed down to a thin piece. For the first time, excitonic transitions have been observed by this method. The room temperature transition energies were evaluated to be 1.48 eV for Eex1and 1.516 eV for Eex 2 . Eex 1 exciton dominates the transition as the polarization is parallel to the b-axis of the layer crystal, while Eex 2 exciton is most present as the polarization is perpendicular. PC spectra are performed to check this anisotropic phenomenon. Thermoreflectance modulation (TR) and photoluminescence (PL) measurements have been performed in the temperature range of 42 to 300 K. The temperature dependence of the transition energies and broadening parameters were determined.