The　short-cut　biological　nitrogen　removal　process　has　been　widely　used　in　industrial　wastewater　treatment,　and　denitrification　is　a　crucial　step　for　removing　nitrogen　on　which　the　effect　of　Cu2+,　a　common　heavy　metal　ion　in　wastewater,　has　not　been　studied.　In　this　study,　sludge　with　good　short-range　biological　nitrogen　removal　characteristics　in　an　A/O　reactor　was　selected　to　investigate　the　short-term　and　long-term　effects　of　Cu2+　on　denitrification　using　NO2-　as　an　electron　acceptor.　The　results　showed　that　Cu2+　had　a　significant　inhibitory　effect　on　denitrification　process　using　NO2-　as　an　electron　acceptor,　and　the　semi-inhibitory　concentration　EC50　of　sludge　activity　was　4.79　mg•L-1.　In　the　long-term　experiment,　the　concentration　of　Cu2+　was　gradually　increased.　When　the　concentration　of　Cu2+　was　0.5　mg•L-1and　1　mg•L-1,　the　denitrification　activity　of　the　sludge　could　be　restored　to　the　original　level　after　acclimation.　When　the　concentration　of　Cu2+　was　increased　to　3　mg•L-1,　the　denitrification　performance　was　destroyed　and　difficult　to　recover,　at　which　point　the　NO2--N　removal　rate　was　reduced　to　less　than　10%　and　the　denitrification　system　was　severely　inhibited.　However,　there　was　some　recovery　of　sludge　denitrification　capacity　after　the　addition　of　Cu2+　had　been　stopped　for　14　days.　At　the　same　time,　during　the　long-term　effect　of　Cu2+,　the　EPS　content　increased,　which　played　an　important　role　in　protecting　the　microorganism　against　Cu2+　toxicity,　and　increased　the　sludge　particle　size　and,　as　a　result,　sludge　sedimentation.　©　2019,　Science　Press.　All　right　reserved.