Heterotrophic　nitrification-aerobic　denitrification　(HN-AD)　process　was　achieved　in　a　moving　bed　biofilm　reactor　after　180-days　acclimation　using　PCL　as　carbon　source　for　low　C/N　wastewater　treatment.　A　novel　HN-AD　strain,　JQ-H3,　with　ability　of　PCL　degradation　was　augmented　to　improve　nitrogen　removal.　TN　removal　efficiencies　of　82.31%,　90.05%,　and　93.16%　were　achieved　in　the　augmented　reactor　(R2),　at　different　HRTs　of　24　h,　20　h,　and　16　h,　while　in　the　control　reactor　(R1),　the　TN　removal　efficiencies　were　59.24%,　74.61%,　and　76.68%.　The　effluent　COD　in　R2　was　10.17　mg/L,　much　lower　than　that　of　42.45　mg/L　in　R1.　Microbial　community　analysis　revealed　that　JQ-H3　has　successfully　proliferated　with　a　relative　abundance　of　4.79%.　Relative　abundances　of　functional　enzymes　of　nitrogen　cycling　remarkably　increased　due　to　bioaugmentation　based　on　the　analysis　of　PICRUSt2.　This　study　provides　a　new　approach　for　enhancing　nitrogen　removal　in　low　C/N　sewage　treatment　via　the　HN-AD　process.