In　recent　years,　more　stringent　environmental　protection　requirements　have　led　to　increasingly　higher　voltage　power　equipment　that　adopt　SF6　mixed　gas　as　an　insulation　medium.　In　this　paper,　the　streamer　development　in　SF6　mixed　gas　and　the　distribution　of　each　gas　component　were　studied　over　time.　Thus,　a　discharge　model　of　the　needle　plate　electrode　with　SF6　mixed　gas　was　established.　The　hydrodynamic　model　for　SF6　mixed　gas　discharge　in　uneven　electric　fields　was　created　by　coupling　the　Boltzmann　drift-diffusion　equation　and　Poisson＇s　equation.　The　influence　of　different　factors,　such　as　the　applied　voltage,　gas　mixture　ratio,　and　electrode　spacing,　on　the　streamer　discharge　of　SF6/N2　mixed　gas,　and　the　influence　of　the　type　of　mixed　gas　(air　and　CO2)　combined　with　SF6　on　the　streamer　development　process　were　studied.　The　simulation　results　showed　that　the　higher　SF6　content　in　the　mixed　gas　made　breakdown　more　difficult,　and　a　higher　pressure　led　to　a　more　concentrated　streamer.　Comparing　and　analyzing　the　discharge　processes　under　different　SF6　mixed　gases　(SF6/CO2,　SF6/air,　and　SF6/N2)　showed　that　the　streamer　for　the　SF6/CO2　mixture　took　longer　to　develop　toward　the　plate　electrode　with　a　more　difficult　breakdown.　The　presented　simulation　results　provide　a　microscopic　interpretation　for　the　needle-plate　discharge　defects　that　appear　in　power　equipment　that　utilize　SF6　mixed　gas.　©　2020　Author(s).