The electronic structure and UV-Vis properties of ground state CuSin (n=4～10) and CuSin anion clusters were studied using B3LYP density functional theory (DFT) at a 6-311+G (d) level. Calculations indicate that: (1) the band gap of neutral CuSin clusters is narrower than their anion, indicating anion clusters are relatively stable; (2) the energy gap and electronic structure calculations indicate that the anion CuSi5 cluster is more stable than neighboring clusters; and (3) the UV-Vis spectrum of CuSin clusters and CuSin anions suggests that the neutral clusters are weakly absorbing; the anion clusters are strongly absorbing, and anion clusters with increasing size of the Si atoms experience a redshift in the absorption spectra.