In　order　to　alleviate　extreme　haze　pollution,　understanding　the　origin　of　fine　particulate　matter　(PM2.5)　is　crucial.　In　this　study,　we　applied　Particulate　Matter　Source　Apportionment　Technology　(PSAT)　in　CAMx　(CoMprehensive　Air　Quality　Model　with　Extensions)　to　quantify　the　impacts　of　emissions　from　different　regions　on　PM2.5　concentrations　in　Beijing　for　haze　episodes　during　January　6-23,　2013.　Emission　inventory　was　developed　by　Tsinghua　University.　Evolution　of　local　and　Regional　contributions　during　local　and　non-local　dominated　haze　episodes　were　discussed,　separately.　In　the　meanwhile,　average　contribution　of　other　every　city　in　Jing-Jiti-Ji　region　to　PM2.5　concentrations　larger　than　75　mu　g　m(-3)　in　Beijing　urban　for　each　range　of　local　contribution　percent　was　analyzed.　The　results　indicate　that　local　emissions　contributed　83.6%　of　PM2.5　at　the　urban　center　of　Beijing,　while　regional　transport　from　surrounding　cities　and　parts　of　Shandong,　Henan　and　Anhui　provinces　contributed　9.4%;　long-range　transport　contributed　the　remaining　7.0%　mainly　from　areas　＞750　km　away　to　the　south　of　Beijing　during　this　study　period.　Compared　to　non-local-dominated　haze　episodes,　local-dominated　heavy　haze　episodes　in　Beijing　were　easily　resulted　from　unfavorable　meteorological　conditions　with　much　lower　PBL　and　wind　velocity.　Furthermore,　local　contribution　is　more　easily　to　cause　a　sharp　increase　or　sharp　reduction　of　PM2.5　concentration　in　central　Beijing,　reflecting　that　Beijing　local　has　much　stronger　potential　to　form　extremely　heavy　haze　episodes.　The　results　indicated　that　controlling　local　emissions　is　a　much　more　important　measure　to　alleviate　the　extreme　haze　episodes　in　Beijing,　like　that　on　the　night　of　Jan　12,　2013.　Furthermore,　emission　control　in　Jinglin-li　region,　especially　in　Tangshan,　Tianjin,　Baoding,　Langfang,　Shijiazhuang　and　Cangzhod,　as　well　as　Henan　and　Shandong　province,　are　important　to　reduce　the　PM2.5　concentrations　and　the　occurrence　of　haze　episodes　in　Beijing.　(C)　2016　Elsevier　B.V.　All　rights　reserved.