Algal-bacterial　granular　sludge　(ABGS)　was　studied　in　a　10　L　sequencing　batch　reactor　(SBR)　for　treating　synthetic　municipal　wastewater.　ABGS　was　rapidly　achieved　within　approximately　15　days.　Algae　provided　the　filamentous　framework　and　promoted　extracellular　polymeric　substance　(EPS)　production,　which　benefited　ABGS　formation.The　removal　rates　of　NH4+-N,　COD,　PO43--P,　and　TN　were　99　%,　92　%,　95　%,　and　78　%,　respectively.　Compared　to　aerobic　granular　sludge　(AGS),　TN　removal　rate　in　ABGS　increased　by　18　%.　During　ABGS　formation　and　stabilization,　major　functional　bacteria,　such　as　glycogen　accumulating　organisms　(GAOs)　and　phosphate　accumulating　organisms　(PAOs),　were　enriched,　while　algae　underwent　succession.　Nitzschia　and　norank_f_norank_o_Chloroplast　replaced　Scenedesmus　and　Auxenochlorella　as　the　predominant　algae.　Furthermore,　there　were　various　mutual　relationships　including　cooperation　and　competition　between　bacteria　and　algae.　Bacillariophyta　positively　correlated　with　major　functional　bacteria,　while　Chlorophyta　negatively　correlated　with　most　functional　bacteria　in　ABGS.　The　interaction　between　bacteria　and　algae　was　crucial　in　ABGS　construction　and　regulation.