The　measurement　of　PM2.5　was　conducted　from　20th　October　to　25th　November　2014,　and　15th　August　to　15th　September　2015　at　Beijing,　Shijiazhuang,　and　Tangshan,　China,　covering　two　important　events　of　Asia-Pacific　Economic　Cooperation　(APEC)　and　Grand　Military　Parade　(Parade).　A　series　of　stringent　emission-reduction　measures　were　implemented　in　Beijing　and　neighbouring　regions　to　ensure　good　air　quality　in　Beijing.　PM2.5　concentrations　and　major　components　(water-soluble　ions　and　carbonaceous　aerosol)　were　analyzed　and　compared　between　the　two　events.　PM2.5　concentration　during　control　demonstrated　a　decreasing　trend　with　51.6%-65.1%　and　34.2%-64.7%　compared　to　no　control　during　APEC　and　Parade,　respectively.　The　water-soluble　ions　and　carbonaceous　aerosol　concentrations　also　decreased　obviously.　The　lower　secondary　inorganic　ions　(SIA,　including　SO42-,　NO3-,　and　NH4+)　percentage　(31.7%-38.3%)　during　control　indicated　the　relative　weak　contribution　of　atmospheric　chemical　processes.　Due　to　the　unfavorable　weather　conditions　and　increased　emissions　during　coal-fired　heating,　the　relative　higher　organic　carbon　(OC),　secondary　organic　carbon　(SOC),　secondary　organic　aerosol　(SOA)　concentrations　during　APEC　was　found.　The　WRF-CMAQ　modeling　system　was　also　used　to　quantify　the　effect　of　emission-reduction　and　different　sources　controls　on　PM2.5.　The　results　indicated　PM2.5　decrease　by　30.4%　and　34.2%　under　control　during　APEC　and　Parade,　respectively.　We　found　that　the　local　emission-reduction　in　Beijing　contributesmore　to　＂APEC　blue＂　(20.8%)　and　＂Parade　blue＂　(25.8%)　in　Beijing　than　those　from　neighbouring　regions　of　Beijing,　and　meteorological　condition　was　more　beneficial　for　the　improvement　of　the　air　quality　during　Parade　than　APEC.　The　emission　source　apportionment　to　PM2.5　in　Beijing　indicated　that　PM2.5　concentration　increased　by　13.5%　and　14.7%　during　APEC　and　Parade,　respectively　if　no　vehicles　emission-reduction　measures　were　taken　in　Beijing.　(C)　2017　Published　by　Elsevier　B.　V.