Under　the　Air　Pollution　Prevention　and　Control　Action　Plan　(APPCAP)　implemented,　China　has　witnessed　an　air　quality　change　during　the　past　five　years,　yet　the　main　influence　factors　remain　relatively　unexplored.　Taking　the　Beijing-Tianjin-Hebei　(BTH)　and　Yangtze　River　Delta　(YRD)　regions　as　typical　cluster　cities,　the　Weather　Research　Forecasting　(WRF)　and　Comprehensive　Air　Quality　Model　with　Extension　(CAMx)　were　introduced　to　demonstrate　the　meteorological　and　emission　contribution　and　PM2.5　flux　distribution.　The　results　showed　that　the　PM2.5　concentration　in　BTH　and　YRD　significantly　declined　with　a　descend　ratio　of　-39.6%　and　-28.1%,　respectively.　For　the　meteorological　contribution,　those　regions　had　a　similar　tendency　with　unfavorable　conditions　in　2013-2015　(contribution　concentration　1.6-3.8　mu　g/m(3)　and　1.1-3.6　mu　g/m(3))　and　favorable　in　2016　(contribution　concentration　-1.5　mu　g/m(3)　and　-0.2　mu　g/m(3)).　Further,　the　absolute　value　of　the　net　flux＇s　intensity　was　positively　correlated　with　the　degree　of　the　favorable/unfavorable　weather　conditions.　When　it　came　to　emission　intensity,　the　total　net　inflow　flux　increased,　and　the　outflow　flux　decreased　significantly　across　the　border　with　the　emission　increasing.　In　short:　the　aforementioned　results　confirmed　the　effectiveness　of　the　regional　joint　emission　control　and　provided　scientific　support　for　the　proposed　effective　joint　control　measures.