In　order　to　investigate　the　effects　of　different　illumination　strategies　in　the　anaerobic　stage　on　the　bacterial-algal　symbiotic　system,　four　groups　of　sequence　batch　reactors　(SBR)　were　set　up　to　operate　in　an　anaerobic/aerobic　(A/O)　mode,　in　which　the　anaerobic　stage　of　R1　was　illuminated　with　8000lx;　R2,　R3　and　R4　divided　the　anaerobic　stage　into　A1　and　A2.　There　is　no　illumination　in　the　A1stage,　and　the　illumination　intensity　in　the　A2stage　respectively　are　0,　3000,　5000lx.　The　results　of　this　research　revealed　that　R3　and　R4　with　weak　illumination　added　at　the　late　anaerobic　stage　could　rapidly　enriched　the　microalgae,　which　led　to　the　formative　bacterial-algal　symbiotic　granular　with　dense　structure,　good　settling　performance,　better　carbon,　nitrogen　and　phosphorus　removal,　and　the　secretion　of　more　extracellular　polymers　(EPS).　Among　them,　R3　had　the　best　effect　of　phosphorus　removal,　and　the　removal　rate　of　total　phosphorus　(TP)　reached　95.87%.　According　to　the　analysis　of　typical　cycle,　the　phosphorus　release　at　the　end　of　anaerobic　stage　was　proportional　to　the　chlorophyll　a　(Chl-a)　content　under　weak　illumination　condition;　the　ability　of　R3　to　release　phosphorus　is　the　strongest,　and　its　phosphorus　concentration　at　the　end　of　anaerobic　stage　reaching　43.73mg/L;　the　high-phosphorus　environment　formed　in　the　A2　stage　was　able　to　stimulate　the　growth　of　microalgae,　and　its　Chl-a　content　reached　6.13mg/gVSS　at　the　late　stage　of　the　operation.　High-throughput　sequencing　showed　that　the　prokaryotic　of　R3　were　successfully　enriched　phosphorus　accumulating　bacteria　(PAOs)　centered　on　Candidatus_Accumulibacter　with　an　abundance　of　11.18%;　the　total　abundance　of　microalgae　in　the　eukaryotes　reached　84.29%,　of　which　the　abundance　of　Halochlorella　was　as　high　as　42.85%,　suggesting　that　the　addition　of　weak　illumination　(3000lx)　to　the　high-phosphorus　environment　in　the　late　anaerobic　stage　could　stimulate　the　growth　of　microalgae　without　affecting　the　growth　of　the　PAOs,　thus　form　a　symbiotic　granular　with　microalgae　and　PAOs　as　the　core,　which　provides　technical　support　for　the　deep　treatment　of　wastewater.　©　2024　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.