The　Upper　Cretaceous　sediments　of　the　southwest　Tarim　Basin　include　the　remnants　of　a　large　epicontinental　sea.　In　this　study,　based　on　the　analyses　of　sedimentation,　foraminifera,　ostracods,　bivalves,　and　other　fossils　from　the　Simuhana　Section,　as　well　as　published　biostratigraphy　data,　we　present　a　field-based　biostratigraphy　and　review　of　sea-level　change　for　the　Upper　Cretaceous　strata　in　the　southwest　Tarim　Basin.　The　Upper　Cretaceous　marine　strata　include　the　Kukebai　and　Dongba　formations.　Relatively　abundant　foraminifera,　ostracods,　and　bivalves　were　discovered　and　identified.　Based　on　the　biostratigraphy　and　correlation,　the　proposed　age　of　the　Lower　and　Middle　Kukebai　Formation　is　Cenomanian　to　earliest　Turonian;　the　Upper　Kukebai　is　of　Turonian　to　early　Coniacian　age.　The　Lower　Dongba　Formation　is　late　Coniacian　to　early　Campanian,　the　Middle　Dongba　Formation　is　late　Campanian　to　early　Maastrichtian,　and　the　Upper　Dongba　Formation　is　late　Maastrichtian　in　age,　possibly　extending　into　the　Danian.　The　relative　sea　level　began　to　rise　during　sedimentation　of　the　Lower　Kukebai　Formation　(Cenomanian),　and　reached　a　maximum　by　the　time　of　the　middle　to　upper　part　of　the　Upper　Kukebai　Formation　(Turonian　to　early　Coniacian).　After　a　subsequent　sea　level　fall,　another　transgression　began　during　sedimentation　of　the　Middle　Dongba　Formation.　Above　the　Upper　Dongba　Formation,　the　sea　level　fell　dramatically.　The　sea　level　of　the　southwest　Tarim　Basin　shows　a　close　relationship　with　the　global　sea　level　curve,　and　with　the　sea　level　of　south　Tibet.　©　2015　Elsevier　B.V.