The　one-stage　nitritation/anammox　(anaerobic　ammonium　oxidation)　process　is　an　energy-saving　technology,　which　has　been　successfully　developed　and　widely　applied　to　treat　industrial　wastewaters.　For　the　one-stage　nitritation/anammox　process,　key　functional　microbes　generally　include　anaerobic　ammonia　oxidation　bacteria　(AnAOB),　ammonia-oxidizing　bacteria　(AOB),　nitrite　oxidizing　bacteria　(NOB),　and　heterotrophic　bacteria　(HB).　Cooperation　and　competition　among　the　key　functional　microbes　are　critical　to　the　stability　and　performance　of　anammox　process.　Based　upon　key　functional　microorganisms,　this　review　summarizes　and　discusses　the　optimized　strategies　that　promote　the　operation　of　one-stage　nitritation/anammox　process.　In　particular,　the　review　focuses　on　strategies　related　to:　(1)　the　retention　of　anammox　biomass　through　granular　sludge　or　biofilm,　(2)　the　balanced　relationship　between　AOB　and　AnAOB,　(3)　the　NOB　suppression　and　(4)　the　HB　management　by　controlling　the　influent　organic　matter.　In　addition,　the　review　proposes　further　research　to　address　the　existing　challenges.