The　characteristics　of　urea　injection　and　NOx　conversion　efficiency　are　closely　related.　A　SCR　test　bench　was　built　based　on　V2O5-WO3/TiO2　catalyst,　and　NO,　NH3　and　O2　feed　streams　were　dosed　by　mass　flow　controllers.　The　effect　of　normalized　stoichiometric　ratio　(NSR)　and　catalyst　temperature　on　ammonia　storage,　ammonia　slip　and　NOx　conversion　efficiency　was　studied.　The　results　show　that　the　influence　of　NSR　and　temperature　on　ammonia　storage,　ammonia　slip　and　NOx　conversion　efficiency　is　obvious.　The　time　of　ammonia　storage　will　be　shorten　with　the　increase　of　NSR,　then　the　improving　speed　of　NOx　conversion　efficiency　is　high.　The　NSR　fix　2.2,　the　NOx　reduction　efficiency　increase　from　0　to　4.3%　within　15　s,　and　the　NOx　reduction　efficiency　increase　from　0　to　8.7%　within　15　s　when　NSR　set　3.0.　The　time　of　ammonia　slip　and　ammonia　storage　are　closely　related,　the　time　of　ammonia　slip　will　be　shorten　with　the　increase　of　NSR.　The　method　of　NSR　from　larger　to　the　smaller　can　increase　ammonia　storage　rate　and　optimize　NOx　conversion　efficiency.　Using　this　injection　method　to　carry　out　the　European　transient　cycle(ETC)　test,　the　brake　specific　emission　of　NOx　reduce　from　8.26　g/(kW·h)　to　1.91　g/(kW·h),　and　the　average　and　peak　value　of　ammonia　are　5×10-6　and　18×10-6,　the　NOx　can　reach　the　National　V　emission　regulations.　©　2018,　Editorial　Department　of　Transaction　of　Beijing　Institute　of　Technology.　All　right　reserved.