In　this　study,　an　anaerobic/anoxic/oxic　(A(2)O)　wastewater　treatment　process　was　implemented　to　treat　domestic　wastewater　with　short-term　atrazine　addition.　The　results　provided　an　evaluation　on　the　effects　of　an　accidental　pollution　on　the　operation　of　a　wastewater　treatment　plant　(WWTP)　in　relation　to　Chemical　Oxygen　Demand　(COD)　and　biological　nutrient　removal.　Domestic　wastewater　with　atrazine　addition　in　3　continuous　days　was　treated　when　steady　biological　nutrient　removal　was　achieved　in　the　A(2)O　process.　The　concentrations　of　atrazine　were　15,　10,　and　5　mg　center　dot　L-1　on　days　1,　2　and　3,　respectively.　The　results　showed　that　atrazine　addition　did　not　affect　the　removal　of　COD.　The　specific　NH4　(+)　oxidation　rate　and　NO3　(-)　reduction　rate　decreased　slightly　due　to　the　short-term　atrazine　addition.　However,　it　did　not　affect　the　nitrogen　removal　due　to　the　high　nitrification　and　denitrification　capacity　of　the　system.　Total　nitrogen　(TN)　removal　was　steady,　and　more　than　70%　was　removed　during　the　period　studied.　The　phosphorus　removal　rate　was　not　affected　by　the　short-term　addition　of　atrazine　under　the　applied　experimental　conditions.　However,　more　poly-hydroxy-alkanoate　(PHA)　was　generated　and　utilized　during　atrazine　addition.　The　results　of　the　oxygen　uptake　rate　(OUR)　showed　that　the　respiration　of　nitrifiers　decreased　significantly,　while　the　activity　of　carbon　utilizers　had　no　obvious　change　with　the　atrazine　addition.　Atrazine　was　not　removed　with　the　A(2)O　process,　even　via　absorption　by　the　activated　sludge　in　the　process　of　the　short-term　addition　of　atrazine.