Human　activities　and　associated　carbon　emissions　are　mainly　concentrated　in　cities.　As　big　cities　usually　offer　more　job　prospects　than　small　cities,　residents　are　increasingly　migrating　from　small　cities　to　big　cities　within　a　country.　During　such　internal　migration　process,　production　and　consumption　patterns　typically　change　and　will　end　up　change　in　ecological　footprint.　However,　the　precise　role　of　internal　migration　in　carbon　emissions　is　still　unclear　as　in-migration　and　out-migration　are　likely　to　result　in　carbon　emission　changes　in　opposite　directions.　Therefore,　we　take　evidence　in　China　in　this　paper　to　evaluate　how　internal　migration　across　cities　influences　carbon　emissions　by　using　the　Index　Decomposition　Analysis　(IDA)　method　to　identify　impacts　of　internal　migration　across　cities　in　China　on　carbon　emission　changes.　We　found　a　positive　impact　of　internal　migration　on　the　national　carbon　emissions,　which　increased　China＇s　aggregate　carbon　emission　by　16%　from　2001　to　2016.　The　positive　impact　of　internal　migration　was　achieved　through　greater　demand　for　energy　services　(e.g.,　transportation,　heating,　cooling,　etc.)　in　big　cities　than　that　in　small　cities.　We　also　found　that　the　positive　impact　of　internal　migration　on　carbon　emissions　was　even　larger　than　that　of　net　population　growth.　We　anticipate　our　findings　help　policy　makers　take　informed　decisions　on　optimizing　city　patterns　for　the　sake　of　achieving　carbon　neutrality　and　sustainable　development.