During　the　military　parade　period　in　2015,　air　quality　in　Beijing　was　analyzed　to　investigate　the　impact　of　regional-scale　air　pollutant　control　strategies　on　Beijing.　Ground-observed　meteorological　data,　regulated　air　pollutant　concentrations,　and　chemical　compositions　of　PM2.5　were　analyzed.　The　results　showed　that　the　average　wind　speed　of　north　wind,　temperature,　relatively　humidity　and　ground-level　atmospheric　pressure　during　the　military　parade　period　were　at　the　same　level　with　the　adjacent　period,　whereas,　frequency　of　north　wind　was　obviously　higher.　In　general,　atmospheric　dispersion　conditions　during　the　military　parade　period　was　more　favorable　than　the　adjacent　period.　The　average　concentrations　of　SO2,　NO2,　O3,　PM10　and　PM2.5　were　2.7,　24.2,　63.2,　27.2　and　19.5　μg/m3,　respectively,　which　decreased　by　26.0%,　31.3%,　24.5%,　59.0%　and　59.4%　compared　with　the　adjacent　period,　respectively.　The　decrease　of　PM2.5　was　the　largest,　indicating　the　combination　effect　of　reduction　of　primate　emission　and　precursor　emission.　OC　concentration　(6.1　μg/m3)　was　the　highest　in　PM2.5　chemical　composition,　followed　by　NH4+　(3.8　μg/m3),　SO42-　(3.4　μg/m3)　and　NO3-　(2.5　μg/m3).　Notably,　secondary　OC　accounted　for　57.6%　of　total　OC　even　with　the　implementation　of　emission　reduction　measures.　The　net　effectiveness　of　the　emission　reduction　measures　was　calculated　through　comparisons　of　concentrations　of　air　pollutants　under　similar　meteorological　conditions.　Through　the　implementation　of　emission　reduction　measures,　concentrations　of　SO2,　O3,　NO2,　PM10,　and　PM2.5　decreased　by　50.0%,　0.7%,　42.1%,　45.7%　and　48.6%,　respectively.　In　addition,　the　mechanisms　of　the　different　variations　of　O3　during　the　APEC　period　and　the　militaryparade　period　were　discussed.　©　2017,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.