Photocatalysts　(g-C3N4-P25)　and　photosynthetic　bacteria　(PSB)　were　encapsulated　in　calcium　alginate　beads　by　self-assembly,　and　its　ability　to　treat　simulated　azo　dyes　-contaminated　wastewater　was　studied.　The　removal　efficiency　by　this　photocatalysis-microorganism　composite　was　94%　for　the　dye　reactive　brilliant　red　X-3B　and　84.7%　for　COD　of　synthetic　wastewater　samples,　which　were　significantly　higher　than　immobilized　photocatalysis　and　PSB.　Intermediates　formed　during　the　oxidation　process　were　analyzed　by　UV-visible　spectrophotometry,　FT-IR　and　gas　chromatography-mass　spectrometry　(GC-MS).　Based　on　the　results,　the　degradation　pathway　was　inferred　as　follows.　First,　the　azo　dye　was　converted　into　aniline　and　phenol　derivatives,　through　combined　photocatalytic　and　biocatalytic　degradation　of　X-3B　by　composites.　Then,　the　aromatic　rings　of　these　products　were　attacked　by　free　radicals　generated　by　the　photocatalyst,　leading　to　the　formation　of　linear　alkyl　compounds　and　preventing　the　inhibition　of　bacterial　metabolism　by　aromatic　hydrocarbon.　Finally,　the　linear　alkyl　products　could　be　degraded　and　mineralized　to　CO2　and　H2O　by　the　photosynthetic　bacteria.　©　2018,　Science　Press.　All　right　reserved.