In　this　study,　we　report　the　effect　of　Zn　doping　on　the　thermoelectric　properties　of　Co1-x　Zn　(x)　SbS0.85Se0.15　solid　solutions　(x　=　0,　0.02,　0.05,　0.08).　The　results　show　the　dimensionless　figure　of　merit　(zT)　increases　from　0.17　to　0.34　at　875　K　for　Co0.95Zn0.05SbS0.85Se0.15　sample,　due　to　the　noticeable　decrease　in　the　lattice　thermal　conductivity　by　introducing　point　defect,　which　is　further　confirmed　by　an　analysis　based　on　the　Debye-Callaway-Klemens　model.　Meanwhile,　the　thermoelectric　power　factor　is　maintained　at　high　temperatures.　This　work　highlights　the　important　role　of　point　defect　in　improving　the　thermoelectric　performance　of　CoSbS-based　compounds.