The　responses　of　microbial　communities　and　antibiotic　resistance　genes　(ARGs)　to　azithromycin　and　copper　combined　pollution　under　gradient　increasing　(from　0.5　to　10　mg/L)　and　decreasing　exposure　(from　10　to　0.5　mg/L)　modes　were　investigated.　Nitrification　was　inhibited　more　obviously　under　gradient　increasing　exposure　mode.　Responses　of　archaeal　community　and　function　structure　were　more　obvious　than　bacteria　under　both　exposure　modes.　The　dominant　bacterial　and　archaeal　compositions　(Hyphomicrobium,　Euryarchaeota,　etc.)　were　affected　by　two　exposure　modes,　except　some　rare　archaea　(Methanoregula　and　Methanosarcina).　There　were　more　positive　correlations　between　bacteria　and　archaea,　and　Nitrospira　was　keystone　genus.　Ammonia-oxidizing　archaea　(0.37-3.06%)　and　complete　ammonia　oxidizers　(Nitrospira_ENR4)　were　enriched,　and　Nitrososphaera_viennensis　was　closely　related　to　denitrifying　genes　(napA/B,　nosZ,　etc.).　50　ARG　subtypes　were　detected　and　specific　ARG　subtypes　(aac,　ImrA,　etc.)　proliferated　in　two　exposure　modes.　Bacteria　and　archaea　were　common　hosts　for　24　ARGs　and　contributed　to　their　shifts.