This　study　aims　to　better　understand　the　effects　of　heavy　metal　enrichment　on　microbiomes　and　resistomes　and　the　source-specific　ecological　risks　of　metals　in　the　sediments　of　an　urban　river.　Geo-accumulation　index　and　enrichment　factor　suggested　the　river　sediments　were　contaminated　by　Cd,　Cu,　Pb,　and　Zn　in　varying　degrees.　High-throughput　sequencing-based　metagenomics　analysis　identified　430　types　of　antibiotic　resistance　genes　(ARGs),　dominated　by　the　multidrug,　MLS,　bacitracin,　quinolone,　and　aminoglycoside　ARGs,　and　52　metal　resistance　genes　(MRGs)　mainly　conferring　resistance　to　zinc,　copper,　cadmium,　lead,　mercury　and　multiple　metals.　Spearman　correlation　analysis　and　Mantel　test　showed　the　heavy　metal　enrichment　exerted　significant　effects　on　the　microbial　community,　ARGs　and　MRGs.　Source　apportionment　using　positive　matrix　factorization　revealed　that　natural　source　(42.8%)　was　the　largest　contributor　of　metals　in　the　river　sediments,　followed　by　urban　activities　(35.4%)　and　a　mixed　source　(21.7%).　However,　when　incorporating　the　apportionment　results　into　a　modified　risk　model　to　evaluate　the　source-specific　ecological　risks,　results　showed　human　activities　dominated　the　risks　of　metals.　Comparatively,　the　urban　activities　majorly　caused　moderateand　considerable　ecological　risks,　while　the　mixed　source　with　respect　to　agricultural　and　industrial　activities　contributed　higher　percentages　on　highand　extremely　highecological　risks.