Recently,　transition　metal　sulfides　(TMS)　have　played　an　important　role　in　many　catalytic　reactions.　In　particular,　they　are　widely　used　in　the　petrochemical　industry,　such　as　the　hydrodesulfurization　(HDS)　and　the　hydrodenitrogenation　(HDN)　processes.　In　this　work,　density　functional　theory　(DFT)　and　coupled　cluster　theory　[CCSD(T)]　calculations　were　used　to　study　the　niobium-mixed　di-nuclear　molybdenum　sulfide　clusters　NbMoSn-/0　(n=3　similar　to　7).　In　our　calculations,　their　ground-state　structures　were　determined　and　the　effects　of　doping　metal,　adjusting　the　sulfur　content　(n)　and　changing　the　charge　states　of　clusters　were　discussed　on　the　geometries,　electronic　structures　and　chemical　bonding　of　NbMoSn-/0　(n=　3　similar　to　7).　NbMoSn-/0　(n=3　similar　to　7)　clusters　can　be　viewed　as　linking　different　sulfur　ligands　to　the　NbMoS2　four-membered　rings.　Among　them,　diverse　poly-sulfur　ligands,　such　as　bridging　S-2,　terminal　S-2　and　terminal　S-3　groups,　emerged　in　the　sulfur-rich　clusters.　Generalized　Koopmans＇　Theorem　was　employed　to　predict　the　vertical　detachment　energies　(VDEs),　and　simulate　the　corresponding　anionic　photoelectron　spectra　(PES).　The　first　VDEs　(VDE1st)　of　NbMoSn-　(n=3　similar　to　6)　increased　gradually　as　a　function　of　n,　and　then　decreased　suddenly　when　the　sulfur　content　(n)　reached　7.　The　VDE1st,　reached　the　maximum　by　4.69　eV　when　the　sulfur　content　equaled　to　6.　The　driving　forces　(-Delta　G)　of　the　reduction　reactions　between　NbMoSn-/0　(n　=3　similar　to　7)　and　H-2　were　evaluated.　The　NbMoS7-　anion　with　the　terminal　S-2(2-)　group　yielded　the　negative　value　of　Delta　G,　which　indicated　that　the　reaction　is　thermodynamically　favored　even　at　the　room　temperature.　We　predicted　that　doping　niobium　into　the　molybdenum　sulfides　may　improve　the　emergence　of　S-2　group　which　may　be　helpful　in　producing　the　coordinatively　unsaturated　sites　(CUS)　under　the　H-2/H2S　atmosphere.　Molecular　orbital　analyses　are　performed　to　improve　our　understanding　on　the　structural　evolution　and　the　chemical　bonding　of　NbMoSn-/0　(n=3　similar　to　7)　clusters.