In　this　study,　PM2.5　samples　were　collected　in　Beijing　and　Shijiazhuang　in　winter,　2014.　The　characteristics　of　PM2.5　and　its　water-soluble　ions　component　were　investigated.　Then　the　WRF-CAMx　modeling　system　was　developed　to　examine　the　regional　transportation　impact　of　PM2.5　and　secondary　inorganic　species　within　the　same　period　of　sample　collection.　The　result　showed　the　concentration　of　PM2.5　in　Beijing　during　sample　collecting　period　was　(116.6±87.0)μg/m3.　Total　water-soluble　ions　concentration　was　(45.3±40.6)μg/m3,　and　the　concentration　of　SO42-,　NO3-　and　NH4+　were　(13.3±13.6)μg/m3,　(14.8±15.1)μg/m3　and　(9.1±7.2)μg/m3,　respectively.　The　PM2.5　pollution　in　Shijiazhuang　was　more　serious　than　Beijing,　which　could　be　found　through　the　result　that　the　concentration　of　PM2.5　in　Shijiazhuang　was　(267.7±166.7)μg/m3.　The　concentration　of　total　water-soluble　ions,　SO42-,　NO3-　and　NH4+　were　(111.8　±104.3)μg/m3,　(36.6±36.5)μg/m3,　(28.5±29.3)μg/m3　and　(25.5±29.8)μg/m3,　respectively.　SOR　and　NOR　in　two　sites　was　0.12,　0.10　(Beijing)　and　0.11,　0.14　(Shijiazhuang),　respectively.　Atmospheric　oxidation　effect　in　winter　was　relatively　weaker.　Heterogeneous　oxidation　was　the　mainly　mechanism　of　aerosol　reaction.　The　simulation　results　showed　the　contribution　of　regional　transportation　to　urban　area　of　Beijing　and　Shijiazhuang　in　January　was　28.1%　and　28.3%,　respectively,　and　the　increased　regional　contribution　were　found　during　heavy　pollution　period.　The　regional　transportation　contribution　of　NO3-　was　much　higher　than　that　of　SO42-　in　both　sites.　©　2016,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.