The　carbon　market　is　a　crucial　market-oriented　tool　in　achieving　carbon　neutrality　and　has　been　adopted　by　many　countries　and　regions.　China　has　established　a　policy　system　covering　eight　carbon　trading　pilots　since　2013　and　has　implemented　effective　practices.　Despite　the　evaluation　of　the　carbon　markets　at　the　national　level,　few　studies　identified　the　carbon　emission　reduction　effect　for　a　specific　region　or　assessed　the　differentiated　characteristics　that　may　significantly　impact　the　development　of　the　carbon　market.　This　study　took　the　Beijing-Tianjin-Hebei　(BTH)　region　as　the　research　sample　and　aimed　to　estimate　the　carbon　emission　reduction　effect　of　the　carbon　market　by　using　a　difference-in-differences　approach.　Our　findings　suggested　that　the　carbon　market　in　the　BTH　region　effectively　reduced　its　carbon　intensity　by　14.04%.　Our　estimations　were　robust　after　using　a　winsorization　panel　or　establishing　a　new　control　group.　Furthermore,　the　results　also　indicated　that　the　carbon　market＇s　effect　on　reducing　carbon　intensity　differs　across　cities　and　shows　an　increasing　trend　yearly.　Relevant　recommendations　for　promoting　carbon　trading　policies　were　proposed.