Co3Sn2S2 has attracted a lot of attention for its multiple novel physical properties,including topological nontrivial surface states,anomalous Hall effect,and anomalous Nernst effect.Vacancies,which play important roles in functional materials,have attracted increasing research attention.In this paper,by using density functional theory calculations,we first obtain band structures and magnetic moments of Co3Sn2S2 with exchange-correlation functionals at different levels.It is found that the generalized gradient approximation gives the positions of Weyl points consistent with experiments in bulk Co3Sn2S2.We then investigate the electronic structures of defects on surfaces with S and Sn terminations which have been observed in experiments.The results show that the single sulfur vacancy on the S-terminated surface introduces localized bond states inside the bandgap near the Fermi level.For di-and tri-sulfur vacancies,the localized defect states hybridize with neighboring ones,forming bonding states as well as anti-bonding states.The Sn vacancy on the Sn-terminated surface also introduces localized bond states,which are merged with the valence bands.These results provide a reference for future experimental investigations of vacancies in Co3 Sn2S2.