The　advanced　computational　fluid　dynamics　(CFD)　software　STAR-CCM+　was　used　to　simulate　a　denitrification　(De-NOx)　project　for　a　boiler　in　this　paper,　and　the　simulation　result　was　verified　based　on　a　physical　model.　Two　selective　catalytic　reduction　(SCR)　reactors　were　developed:　reactor　1　was　optimized　and　reactor　2　was　developed　based　on　reactor　1.　Various　indicators,　including　gas　flow　field,　ammonia　concentration　distribution,　temperature　distribution,　gas　incident　angle,　and　system　pressure　drop　were　analyzed.　The　analysis　indicated　that　reactor　2　was　of　outstanding　performance　and　could　simplify　developing　greatly.　Ammonia　injection　grid　(AIG),　the　core　component　of　the　reactor,　was　studied;　three　AIGs　were　developed　and　their　performances　were　compared　and　analyzed.　The　result　indicated　that　AIG　3　was　of　the　best　performance.　The　technical　indicators　were　proposed　for　SCR　reactor　based　on　the　study.Implications:　Flow　filed　distribution,　gas　incident　angle,　and　temperature　distribution　are　subjected　to　SCR　reactor　shape　to　a　great　extent,　and　reactor　2　proposed　in　this　paper　was　of　outstanding　performance;　ammonia　concentration　distribution　is　subjected　to　ammonia　injection　grid　(AIG)　shape,　and　AIG　3　could　meet　the　technical　indicator　of　ammonia　concentration　without　mounting　ammonia　mixer.　The　developments　above　on　the　reactor　and　the　AIG　are　both　of　great　application　value　and　social　efficiency.