In this paper, some electronic properties such as density of states, band structure and optical properties such as the dielectric function, energy loss function, refractive index, optical reflectivity, and absorption coefficient have been calculated based on the density functional theory (DFT) approach. Calculations for CuTaS3 structure show that the main electronic states in the valence band are due to the Cu-3d and S-3p orbitals and the major states in the conduction band are due to the Ta-5d and S-3p orbitals. Calculated band structure shows that CuTaS3 structure is a semiconductor with a direct narrow band gap equal to 0.8 eV which is in good agreement with experimental data. The calculated static refractive indexes of the CuTaS3 structure are equal to 2.65, 3.02, and 2.70 in the x-, y-, and z-directions, respectively. The calculated plasmon energies for CuTaS3 structure are equal to 20.42, 20.72, and 21.21 eV in the x-, y-, and z-directions, respectively. Our results show that in the visible light spectra range (1.8-3.1 eV), the optical reflectivity in the x-direction is lower than other directions, and the optical reflectivity in the y- and z-directions is approximately constant in the all range of the visible light spectrum, the absorption coefficient in the y-direction is approximately larger than other directions.