The　variations　in　concentration　and　diameter　distribution　of　newly　formed　particulate　matter,　during　the　gas-to-solid　conversion　of　the　SO2-NO2-NH3-H2O　quaternary　system,　were　experimentally　investigated　with　the　smog　chamber　in　this　article.　This　quaternary　system　had　a　significant　capability　of　nucleation,　and　a　large　nucleation　intensity　in　such　a　short　duration.　When　both　of　SO2　and　NO2　concentrations　were　200mg/m3　and　NH3　concentration　was　12×10-6,　the　total　concentration　of　aerosols　in　this　system　reached　a　peak　of　2.5×106cm-3　over　two　minute.　Moreover,　the　nucleation　strength　of　the　aerosol　would　be　reduced　lacking　in　any　one　among　three　gases.　Like　this　typical　condition　that　SO2,　NO2　or　NH3　concentration　was　zero,　the　maximum　concentration　of　aerosols　decreased　by　41.0%,　83.6%　and　98.5%,　respectively.　Within　the　concentration　ranges　of　SO2,　NO2　or　NH3　emitted　from　coal-fired　power　plants,　the　NO2　had　a　greater　influence　than　SO2　on　the　formation　and　agglomeration　of　newly　formed　particles.　Based　on　experimental　results,　the　fitting　curves　for　nucleation　characteristics　of　particulate　matters　were　made.　A　linear　correlation　was　observed　between　the　total　number　concentration　of　newly　formed　particles　and　median　particle　diameter,　and　gaseous　pollutant　concentrations.　The　Brown　agglomeration　model　was　adopted　to　simulate　the　changes　in　total　number　concentration　and　particle　size　distribution　of　aerosols　after　nucleation　in　the　agglomeration　process.　Finally,　a　method　was　proposed　for　predicting　the　change　in　the　particle　size　distribution　and　total　number　concentration　of　aerosol　particles,　based　on　the　typical　emission　concentrations　of　SO2,　NO2　and　NH3　from　coal-fired　power　plants.　©　2019,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.