The　simultaneous　partial　nitrification　and　anammox　(PN/A)　granular　sludge　process　in　a　plug-flow　reactor　has　been　difficult　to　achieve.　This　study　provides　a　novel　way　to　enhance　granulation　using　biofilm　detachment.　In　a　plug-flow　reactor,　a　fixed　carrier　was　added　to　the　activated　sludge,　and　a　PN/A　biofilm　gradually　formed　during　the　operation.　Mature　biofilm　detachment　appeared　and　caused　the　emergence　of　micro-granule.　Then　the　fixed　carriers　were　removed　from　the　reactor,　but　the　nitrogen　removal　rate　(NRR)　of　the　reactor　was　barely　affected.　This　result　suggests　granular　sludge　is　a　feasible　replacement　for　biofilm.　Moreover,　the　particle　size　of　the　granule　increased　from　212　to　425　mu　m,　and　the　NRR　was　1.63　kg　N/(m3.d),　with　a　maximum　nitrogen　removal　efficiency　of　86.5%.　Overall,　this　study　implies　that　it　is　feasible　to　maintain　granular　sludge　in　a　plug-flow　PN/A　reactor,　and　biofilm　detachment　significantly　favors　the　granulation　process.