A　sequencing　batch　reactor　and　a　continuously　stirred　tank　reactor　were　used　to　start　the　bacterial-algal　symbiotic　granular　sludge　system　for　the　investigation　into　the　impact　of　different　operation　modes,　including　the　differences　in　algal　content,　pollutant　removal　performance　and　microorganisms　in　the　two　systems.　The　results　showed　that　the　spatial　distribution　of　algae　in　the　bacterial-algal　symbiotic　granular　sludge　was　different　in　the　two　operation　modes,　and　the　algae　in　the　SBR　system　acted　the　inner　layer　and　the　bacteria　were　mainly　distributed　in　the　outer　layer,　and　the　granules　were　more　likely　to　disintegrate　when　the　external　environment　changed.　While　the　algae　in　the　CSTR　system　were　uniformly　distributed　throughout　the　granules,　and　the　filamentous　bacteria　were　able　to　act　as　a　skeletal　network　to　trap　suspended　algae　and　bacteria　in　the　granulation　process,　which　facilitated　the　enrichment　of　algae　and　rapid　granulation　of　sludge.　The　removal　pathway　of　total　inorganic　nitrogen　differed　between　the　two　modes　of　operation,　which　was　dominated　by　functional　bacteria　in　the　SBR　system,　while　dominated　by　algae　assimilation　in　the　CSTR　system　due　to　the　inhibition　of　nitrite　oxidizing　bacteria　with　better　removal　efficiency.　The　removal　rates　of　chemical　oxygen　demand,　total　phosphorus　and　total　inorganic　nitrogen　in　the　CSTR　system　were　about　96%,　96%　and　60%　at　the　end　of　the　experiment.　The　microbial　communities　were　different　between　the　two　modes　of　operation,　with　more　algal　species　and　higher　abundance　in　the　CSTR　system　and　more　functional　bacteria　in　the　SBR　system.　©　2023　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.