An　Aerodyne　Aerosol　Chemical　Speciation　Monitor　ACSM　was　deployed　to　continuously　monitor　the　concentrations　of　non-refractory　submicron　particulate　matter　NR-PM1　and　its　species　in　March,　August,　October　and　December　representing　spring,　late　summer,　autumn,　and　winter,　respectively,　in　the　southeast　urban　area　of　Beijing.　The　evolution　characteristics　of　NR-PM1　and　its　species　in　different　periods,　especially　during　the　haze　days,　and　the　sources　of　organic　aerosol　OA　in　the　four　seasons　were　investigated.　The　results　showed　that　the　average　concentration　of　NR-PM1　was　22.06µg/m3　in　the　whole　study　period.　The　seasonal　variation　of　NR-PM1　mass　concentrations　followed　the　order　of　spring　＞　winter　＞　autumn　＞　late　summer.　In　the　study　period,　the　average　concentration　of　Org　was　7.12µg/m3,　accounting　for　32.30%　of　NR-PM1;　the　average　concentrations　of　NO3-　and　SO42-　were　5.91　and　6.20µg/m3,　respectively,　accounting　for　26.80%　and　28.12%　of　NR-PM1　respectively;　however,　the　average　mass　concentrations　and　mass　fractions　of　both　NH4+　and　Cl-　were　lower.　All　species　concentrations　showed　the　order　of　Org　＞　SO42-　~　NO3-　＞　NH4+　＞　Cl-.　NR-PM1　in　clean　days　was　mainly　characterized　by　Org,　and　the　diurnal　variations　of　all　species　in　each　season　were　smaller.　However,　NR-PM1　in　haze　days　was　mainly　characterized　by　secondary　inorganic　species,　and　each　species　showed　different　diurnal　variations　in　different　seasons.　OA　species　apportioned　in　different　seasons　were　slightly　different.　The　contributions　of　primary　OA　(POA)　to　OA　gradually　increased　in　the　order　of　spring　＜　late　summer　＜　autumn　＜　winter,　but　secondary　OA　(SOA)　to　OA　gradually　decreased.　©　2022　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.