The　risks　of　cross-infection　among　occupants　will　be　greatly　increased　by　the　high　occupant　densities　and　mobility　inside　and　outside　university　classrooms.　In　order　to　know　the　distribution　characteristics　of　culturable　bacterial　aerosols　in　such　public　environments,　during　normal　didactic　activities,　indoor　and　outdoor　bacterial　aerosols　were　sampled　from　December　2018　to　December　2019　by　using　Andersen　six-stage　impactor　in　11　university　classrooms.　The　yearly　average　concentration　of　outdoor　bacterial　aerosols　was　314　+/-　229　CFU/m(3),　and　the　size　mainly　distributed　within　2.1-4.7　mu　m.　For　unoccupied　condition,　indoor　culturable　bacterial　aerosols　were　dominated　by　outdoors　(R-2　=　0.78),　the　yearly　average　concentration　was　254　+/-　130　CFU/m(3),　and　the　size　mainly　distributed　within　1.1-3.3　mu　m.　For　occupied　condition,　the　yearly　average　concentration　of　indoor　bacterial　aerosols　was　494　+/-　263　CFU/m(3),　and　the　size　mainly　distributed　in　the　range　of　1.1-4.7　mu　m.　With　human　presence,　occupants　instead　of　outdoor　air　becoming　the　primary　source　of　indoor　culturable　bacterial　aerosols.　The　seasonal　emission　rates　of　bacterial　aerosols　resulted　from　occupants　were　in　the　order　of　summer　＞　autumn　＞　spring　＞　winter,　corresponding　to　1538　+/-　646,　850　+/-　292,　592　+/-　254,　and　388　+/-　219　CFU/person/h.　Air　temperature,　relative　humidity,　and　PM10　mass　concentrations　were　main　environmental　factors　(p　＜　0.01)　to　positively　influence　the　concentrations　distribution　of　indoor　culturable　bacterial　aerosols.　The　results　can　provide　basic　data　for　evaluating　the　risks　of　occupants　expose　to　bacterial　aerosols　and　improving　indoor　microbial　air　quality　in　university　classrooms.