This　experiment　focuses　on　the　wasted　sludge　from　municipal　sewage　treatment　plants.　Batch　texts　were　taken　to　explore　the　effects　of　different　pH　regulation　methods,　which　include　constant　pH　adjustment　with　values　of　5,7,9,10　and　phased　pH　adjustment,　on　the　dissolution　of　organic　matter　in　anaerobic　fermentation.　The　variations　of　microbial　community　structure　of　fermentation　sludge　under　different　pH　adjustment　conditions　were　analyzed　by　High-throughput　sequencing　technology.　Results　showed　that　more　organic　matter　could　be　dissolved　under　both　alkaline　and　acidic　conditions　with　constant　pH　adjustment,　and　the　accumulation　reached　the　maximum　when　pH　value　was　10.　At　this　point,　solluted　chemical　oxigen　demand　(SCOD)　concentration　was　323.77mg/gVSS,　and　the　VFAs　was　183.38mgCOD/gVSS.　In　the　case　of　phased　pH　adjustment,　a　constant　pH　of　10was　controlled　only　in　the　initial　stage　of　fermentation　(the　first　4days)　and　the　pH　value　was　naturally　reduced　in　the　later　stage,　this　method　showed　more　conducive　to　the　production　of　VFAs　in　the　acid　production　stage.　This　maximum　yield　was　208.78mgCOD/gVSS,　which　was　13.90%　higher　than　the　maximum　total　VFAs　of　same　pH　value　but　with　constant　pH　adjustment.　At　the　phylum　level,　significant　differences　in　microbial　abundance　appeared　after　different　pH　adjustment　operations,　but　the　main　dominant　microorganisms　were　still　Firmicutes,　Proteobacteria,　Actinobacteriota　and　Chloroflexi.　Under　constant　pH　regulation,　the　relative　abundance　of　Firmicutes　and　Actinobacteriota　reached　61.14%　and　15.57%　when　pH　value　was　10,　which　was　the　highest　beyond　other　pH　values.　As　for　the　phased　pH　regulation,　the　relative　abundance　of　Firmicutes　and　Actinobacteriota　increased　to　68.46%　and　18.43%　respectively,　which　grew　more　proportion　than　the　condition　of　constant　pH　adjustment　mentioned　above.　At　the　genus　level,　the　bacterial　abundance　related　to　hydrolytic　acidification　(Proteiniclasticum,　Bacillus,　Acetoanaerobium,　Proteocatella　and　Alkaliphilus,　etc.)　accounted　for　32.38%　when　pH　value　was　constantly　10,　and　51.62%　under　phased　regulation.　The　phased　pH　regulation　improved　the　relative　abundance　of　hydrolytic　acidifying　bacteria　and　was　more　contributive　to　the　accumulation　of　VFAs　during　fermentation.　©　2023　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.