In　municipal　wastewater　treatment,　controlling　the　stability　and　efficiency　of　the　anaerobic　process　is　the　premise　and　key　to　the　high-standard　discharge　of　organic　matter　and　total　nitrogen.　In　this　study,　two　types　of　hydrolytic　acidification,　immobilized　biological　active　fillers　and　traditional　activated　sludge,　were　used　to　treat　municipal　wastewater　at　different　temperatures　(13−24)　and　working　conditions.　The　degradation　of　organic　matter　and　the　transformation　of　organic　nitrogen　in　the　anaerobic　process　were　compared,　and　the　internal　flora　of　the　immobilized　fillers　was　systematically　analyzed　by　high-throughput　sequencing　technology.　The　results　show　that　the　filler　exhibited　higher　activity　at　low　temperatures,　and　the　residual　organic　nitrogen　level　in　the　effluent　(0.3−0.5　mg　L−1)　was　significantly　lower　than　that　in　the　sludge　reactor　(0.8–1.2　mg　L−1).　The　performance　of　hydrolysis-acidification　of　skeleton-less　fillers　(EB3)　was　higher　than　that　of　skeletoned　fillers　(EB2)　(the　hydraulic　retention　time　was　1　h　and　fill　rate　was　8%).　The　organic　nitrogen　of　fillers　was　completely　converted,　while　the　volatile　fatty　acid　of　EB3　effluent　increased　by　2–2.5　mg　L−1,　greater　than　the　increase　in　EB2　effluent　(0.9–1.3　mg　L−1).　Based　on　the　results　of　high-throughput　sequencing,　the　fillers　contained　the　same　functional　species,　albeit　at　different　abundances.　The　immobilized　fillers　could　improve　the　performance　of　traditional　activated　sludge　to　maintain　biomass　through　reflux　and　achieved　the　dual　advantages　of　fixing　biomass　and　maintaining　good　anaerobic　characteristics.　©　2020　Institution　of　Chemical　Engineers