The　study　investigated　the　effects　of　pH　on　a　biological　desulfurization　reactor＇s　performance,　biomass,　and　microbial　structure.　Using　a　bio-trickling　filter　(BTF),　it　operated　under　neutral-alkaline　(6.　0　＜　pH　＜　9.　5),　mildly　acidic　(2.　6　＜　pH　＜　5.　5),　and　extremely　acidic　(pH　＜　1.　0)　conditions,　respectively.　Maximum　H2　S　elimination　capacities　achieved　were　246.　5,　142.　8　and　164.　6　g　/　(m3·h),　respectively.　The　BTF　performed　best　under　neutral-alkaline　condition　due　to　reduced　H2　S　gas-liquid　mass　transfer　resistance　and　increased　activity　of　sulfur-oxidizing　bacteria,　however,　this　required　significant　alkaline　reagents,　raising　costs　and　complicating　the　process.　In　extremely　acidic　condition,　acidophilic　sulfur-oxidizing　bacteria,　Mycobacterium,　became　dominant　(79.　2%),　and　the　biofilm　possessed　high　sulfur-oxidizing　activity　(with　specific　oxygen　uptake　rate　of　1.　35　mg　/　(g·min))　.　Nonacid-tolerant　microbes　were　eliminated,　preventing　reactor　clogging　and　reducing　biomass　control　and　pH　adjustment　costs.　Thus,　by　enriching　acidophilic　Mycobacterium,　BTF　can　maintain　high　desulfurization　performance　under　highly　acidic　conditions,　broadening　the　operational　pH　range　of　biological　reactors.　©　2023　Beijing　University　of　Technology.　All　rights　reserved.