The　WRF-CMAQ　modeling　system　was　employed　to　investigate　the　impact　of　meteorological　conditions　and　emission　reduction　on　PM2.5　pollution　in　China.　The　results　indicate　that　the　PM2.5　concentration　observed　in　2016　and　2017　decreased　by　7%　and　14%,　respectively　compared　with　that　in　2015,　indicating　an　evident　improvement　in　air　quality.　In　2016,　the　decrease　in　PM2.5　concentration　owning　to　meteorological　factor　and　emission　reduction　were　estimated　to　be　4%　and　3%,　respectively.　The　impact　of　meteorological　factors　in　2017　showed　little　difference　compared　with　that　in　2015,　which　implied　that　the　decrease　of　emissions　was　the　decisive　factor　to　PM2.5　decline.　In　the　key　regions　except　for　the　Fenwei　Plain,　such　as　Beijing-Tianjin-Hebei　and　surrounding　region　(＇2+26＇　region),　the　Yangtze　River　Delta　(YRD),　the　Pearl　River　Delta　(PRD)　region　and　the　Chengdu-Chongqing　(CYB)　region,　the　observational　concentration　decreased　steadily.　In　the　PRD　region,　an　increase　of　29%　in　PM2.5　concentration　in　2017　could　be　attributed　to　the　variations　of　meteorological　conditions.　Except　for　the　FenWei　plain,　the　decrease　of　emissions　contributed　to　a　larger　drop　in　PM2.5　concentration　in　2017　in　the　other　key　regions.　The　results　indicated　that　the　emission　cuts　generally　improved　the　air　quality.　The　analytical　methods　presented　in　this　paper　could　be　referred　when　setting　air　quality　goals　or　estimating　environmental　benefit　of　pollution　control　plans.　©　2019,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.