WRF-CAMx　modeling　system　was　developed　to　examine　the　regional　transportation　of　PM2.5　and　secondary　inorganic　aerosol　(SIA)　in　Beijing-Tianjin-Hebei　(BTH)　and　its　surrounding　provinces.　Regional　emission　contribution　to　the　PM2.5　and　SIA　of　BTH　was　estimated,　and　the　transmission　matrix　among　different　provinces　was　also　obtained.　Results　showed　that　regional　transmission　effect　of　PM2.5　and　SIA　components　was　comparatively　significant.　PM2.5　and　SIA　of　BTH　contributed　by　emissions　from　outside　region　was　23.4%　and　45.5%,　respectively.　Local　emissions　contributed　51.2%~68.8%　of　the　annual　average　PM2.5　and　36.7%~56.4%　of　the　SIA　in　each　province　and　city.　Sources　of　the　four　severe　pollution　processes　in　January　2013　of　Beijing　were　analyzed　combining　backward　trajectory　model;　and　it　was　found　that　the　sources　were　quite　different　from　each　other,　including　long　distance　transportation　from　northwest　direction,　short　distance　transportation　from　the　south　and　local　air-mass　transportation　from　southwest　and　southeast.　Regional　transportation　was　more　obviously　during　the　severe　pollution　processes,　PM2.5　and　SIA　contributed　by　local　emissions　were　only　35.1%~37.3%　and　17.1%~28.4%,　respectively.　Among　that,　air-mass　transported　from　southern　part　could　lead　to　higher　pollution　level;　and　the　contributions　from　emissions　of　BTH　was　remarkable,　they　reached　83.2%　and　76.4%　for　PM2.5　and　SIA,　respectively.　©　2016,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.