Surface　modification　of　polymeric　materials　based　on　non-equilibrium　plasma　fed　with　helium　(He)　and　tetrafluoromethane　(CF4)　has　gained　much　attention.　In　this　paper,　an　atmospheric　pressure　plasma　jet　(APPJ)　generated　in　He/CF4　mixtures　is　developed,　and　it　is　characterized　systematically　by　electrical　and　optical　methods.　It　is　found　that　the　He/CF4　APPJ　presents　three　kinds　of　discharge　modes,　i.e.,　glow　discharge,　unstable　glow　discharge,　and　filamentary　discharge　under　different　operation　parameters　including　applied　voltage　and　gas　composition.　With　the　increase　in　applied　voltage,　the　discharge　mode　transits　from　glow　to　filamentary　discharge　gradually,　while　the　gas　composition　has　significant　influences　on　ignition/extinction　voltages　and　excited　species.　The　discharge　modes　under　different　parameters　are　obtained,　and　the　applied　voltage　is　regarded　as　the　main　reason　for　discharge　mode　transition.　The　excited　species　in　the　He/CF4　APPJ　mainly　include　the　excited　helium　atoms,　the　fluorine　groups,　and　the　impurities　originated　from　air,　whose　generation　reactions　are　discussed.　The　evolution　of　excited　species　under　different　parameters　and　discharge　modes　is　acquired.　The　discharge　modes　and　excited　species　of　the　He/CF4　APPJ　can　be　well　modulated　by　changing　applied　voltage　and　CF4　volume　fraction.　Published　by　AIP　Publishing.