DC　cables　operate　under　high　temperature　gradients　for　a　long　time　and　are　often　subjected　to　transient　voltages　such　as　polarity　reversal　and　impulse　voltage,　et　al.,　which　seriously　threatens　the　reliability　of　cable　insulation.　In　this　paper,　silicone　rubber,　the　main　insulation　material　for　cable　accessories　was　selected,　and　electrical　tree　initiation　characteristics　with　varied　temperature　gradient　under　polarity　reversal　voltage　were　studied.　A　bipolar　carrier　transport　model　under　extremely　inhomogeneous　fields　was　built,　and　the　charge　transportation　and　electric　field　distribution　characteristics　during　different　temperature　gradients　and　polarity　reversal　voltages　were　studied.　Results　show　that　as　the　temperature　of　needle　tip　rises,　the　amount　of　space　charge　injection　and　the　depth　of　injection　continue　to　increase　and　the　electric　field　changes　more　after　the　reversal.　When　the　temperature　increases　from　30　to　120,　the　tree　initiation　voltage　decreases　by　26.2%,　and　the　tree　morphology　tends　to　be　dense,　but　the　tree　length　first　increases　and　then　decreases.　Combined　with　the　characteristics　of　space　charge　transportation,　the　initiation　process　of　electrical　tree　under　polarity　reversal　was　given,　and　the　influence　of　temperature　gradient　on　tree　initiation　characteristics　was　analyzed.　©　2022　Chin.　Soc.　for　Elec.　Eng.