Mixing　helium　and　argon　as　the　working　gas　of　cold　plasma　jets　has　a　great　application　potential,　however,　the　research　on　helium-argon　plasma　jet　is　very　scarce,　and　intensive　study　is　urgently　needed.　Therefore,　the　effects　of　different　ratios　of　helium　and　argon　in　the　working　gas　of　the　helium-argon　plasma　jet　on　the　discharge　characteristics　and　reactive　species　were　studied　in　this　paper.　The　results　show　that　changing　the　ratio　of　helium　and　argon　in　the　working　gas　will　significantly　affect　the　discharge　morphology　of　helium-argon　plasma　jet.　When　the　argon　volume　fraction　is　less　than　10%,　the　penning　effect　between　He　and　Ar　is　the　strongest,　the　discharge　is　the　most　stable,　and　the　plasma　jet　length　is　twice　that　of　the　plasma　jet　produced　by　the　other　argon　volume　fractions.　With　the　increase　of　the　argon　volume　fraction,　the　breakdown　voltage　of　helium-argon　plasma　jet　gradually　increases;　especially,　when　the　argon　volume　fraction　is　30%,　the　breakdown　voltage　is　twice　that　when　the　argon　volume　fraction　is　0.　When　the　working　gas　is　doped　with　argon,　the　reactive　species　in　the　gas　phase　are　almost　the　same,　only　differ　in　the　intensity　of　the　spectral　lines.　The　area　of　the　surface　distribution　of　the　reactive　species　on　the　model　human　tissue　will　increase　with　the　growth　of　the　argon　volume　fraction　in　the　working　gas,　especially　when　the　argon　volume　fraction　is　30%,　the　area　is　four　times　that　when　the　argon　volume　fraction　is　0.　©　2022　Science　Press.　All　rights　reserved.