The　effects　of　the　Administrative　Examination　and　Approval　System　Reform　on　economic　growth　and　entry　of　businesses　have　drawn　much　attention.　However,　few　scholars　pay　attention　to　the　impacts　of　this　policy　on　SO2　emissions.　Keeping　in　view　the　existing　research　gap,　a　spatial　difference-in-difference　(SDID)　model　is　employed　to　assess　the　effects　of　the　Administrative　Examination　and　Approval　System　Reform　on　SO2　emissions　in　297　Chinese　cities　during　the　period　1995-2020　from　the　perspective　of　spatial　spillover　effects.　The　results　show　that　the　establishment　of　Administrative　Examination　and　Approval　Center　(AEAC)　has　significantly　positive　effects　on　the　local　SO2　emissions.　The　significant　indirect　(spatial　spillover)　effects　are　confirmed.　That　is,　the　establishment　of　AEAC　of　a　given　city　has　a　significant　positive　impact　on　the　SO2　emissions　of　neighboring　cities.　The　findings　are　confirmed　by　several　robustness　tests.　Our　study　findings　have　significant　implications　for　the　cross-border　coordination　of　environmental　policies　that　aim　to　improve　the　quality　of　the　environment　across　borders.