Given　the　imperative　of　fostering　synergistic　environmental　and　economic　development,　investigating　the　cost-effectiveness　of　environmental　policies　in　reducing　pollutant　and　carbon　emissions　holds　significant　importance.　This　research　evaluates　the　marginal　abatement　costs　(MAC)　of　carbon　and　pollutants　in　30　Chinese　provinces　from　2000　to　2019.　Then,　a　difference-in-difference　(DID)　model　is　used　to　evaluate　the　direct　effect　of　the　carbon　emission　trading　system　(CTES)　on　MAC,　and　its　dynamic　change　properties　are　examined.　The　indirect　effect　of　CETS　on　MAC　is　next　examined　from　the　standpoint　of　abatement　space　and　technological　progress,　and　lastly,　the　total　effect　is　taken　into　consideration.　The　findings　indicate　that:　(i)　The　measured　MAC　exhibits　variations　based　on　time　and　location.　(ii)　The　CETS　has　a　synergistic　effect,　lowering　both　the　marginal　abatement　costs　of　pollutants　(PMAC)　and　the　marginal　abatement　costs　of　carbon　(CMAC),　especially　the　former.　(iii)　The　CETS　tends　to　have　a　steadily　diminishing　effect　on　MAC　over　time.　(iv)　The　CETS　not　only　reduces　carbon　and　pollutant　emissions,　but　indirectly　affects　MAC　through　technological　progress　and　abatement　space,　and　the　indirect　effect　had　a　stronger　impact　on　PMAC　compared　to　CMAC.　Based　on　the　study＇s　findings,　policy　proposals　are　put　forth　to　encourage　the　cost-based　synergy　of　pollution　and　carbon　emissions　reduction.