©　2018　Author(s).　The　optical　emission　spectrum　of　the　propagating　current　sheet　in　a　small-bore　parallel-plate　electromagnetic　plasma　accelerator　has　been　studied.　The　accelerator　is　powered　by　a　fourteen　stage　pulse　forming　network,　which　yields　a　damped　oscillation　square　wave　of　current　with　a　pulse　width　of　20.5　μs.　The　movement　of　the　first　current　sheet　and　the　second　current　sheet　is　identified　using　three　single　magnetic　probes　placed　at　various　axial　positions.　Current　sheet　canting　is　measured　by　two　double　magnetic　probes.　The　spectrum　of　the　current　sheet　is　measured　using　a　spectroscopic　system.　The　electron　density　of　the　current　sheet　plasma　is　determined　via　Stark　broadening　of　the　hydrogen　Hα　line.　The　current　sheet　is　almost　perpendicular　to　the　electrode.　The　current　sheet　electron　density　increases　as　the　current　sheet　propagates.　The　current　sheet　electron　density　is　mainly　determined　by　the　prefill　pressure　rather　than　the　discharge　current.　The　impurity　charged　particles　caused　by　ablation　of　the　back　wall　insulator　exists　in　the　current　sheet.　Residual　particles　are　generally　left　behind　the　first　current　sheet　and　are　swept　and　ionized　by　the　second　current　sheet.　The　estimated　current　sheet　sweeping　efficiency　is　greater　than　80%.　The　parallel-plate　electromagnetic　plasma　accelerator　developed　in　this　paper　shows　great　potential　in　generating　high　electron　density　plasma　jets.