In　this　study,　the　characteristics　of　fine　particles　before　and　after　wet　flue　gas　desulfurization　(WFGD)　in　three　coal-fired　heating　boilers　in　northern　China　were　investigated　by　using　a　dilution-based　emission　sampling　experimental　system.　The　influences　of　the　WFGD　process　on　the　mass　and　number　concentrations　as　well　as　the　chemical　composition　of　fine　particles　were　analyzed.　The　removal　efficiency　of　desulfurization　processes　on　particulate　matter　mass　was　30.06%-56.25%　for　the　three　study　units.　The　WFGD　had　a　great　influence　on　the　size　distributions　of　particle　mass　concentration　and　number　concentration.　A　significant　increase　in　the　number　and　mass　concentration　of　particles　in　the　size　range　of　0.094-0.946　mu　m　was　observed.　The　watersoluble　ion　content　accounted　for　a　very　large　proportion　of　PM2.5　mass,　and　its　proportion　in　PM2.5　increased　from　28.39%-41.08%　to　48.96%-61.21%　after　the　WFGD　process　for　the　three　units.　The　desulfurizing　process　also　drastically　increased　the　proportion　of　cation　component　(Ca(2)(+)for　unit　A,　Mg2+　for　unit　B,　and　Na+　for　unit　C)　and　the　proportion　of　SO42-　in　PM2.5　,　and　it　increased　the　CE/AE　values　of　PM2.5　from　0.82-0.98　to　0.93-1.27　for　the　three　study　units.　(C)　2018　The　Research　Center　for　Eco-Environmental　Sciences,　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.