To　provide　insights　into　the　Early　Paleozoic　tectonic　evolution　of　the　southern　portion　of　the　long-lived　Central　Asian　Orogenic　Belt,　we　have　conducted　major　and　trace　element　analyses　and　zircon　U-Pb　dating　of　granitoid　samples　from　central　Inner　Mongolia.　Our　study　area　covers　three　pre-Mesozoic　tectonic　units　from　north　to　south:　the　Wenduermiao　subduction-accretionary　complex,　the　Bainaimiao　magmatic　belt,　and　the　northern　margin　of　the　North　China　craton.　Our　new　geochronological　and　geochemical　data　show　the　temporal　and　genetic　relationships　between　the　three　tectonic　units.　Accordingly,　we　suggest　that　the　Wenduermiao　subduction-accretionary　complex　developed　in　the　Middle　Cambrian-Late　Silurian　(509-421　Ma),　comprising　of　coeval　oceanic　crust,　arc　magmatism,　and　forearc　deposits.　The　Bainaimiao　continental　arc　was　developed　during　the　Late　Cambrian　to　Early　Silurian　(501-437　Ma),　which　superposed　on　the　basement　with　the　affinity　of　the　North　China　craton.　The　back-arc　basin　opened　prior　to　Early　Silurian　and　lasted　to　the　Late　Silurian,　which　is　slightly　younger　than　Bainaimiao　island　arc.　The　Wenduermiao　Ocean,　between　the　Wenduermiao　subduction-accretionary　complex　and　the　Bainaimiao　continental　arc,　existed　in　Early　Paleozoic.