The　silicone　rubber(SR)　insulated　cable　joint　contains　a　composite　interface　between　cross-linked　polyethylene(XLPE)　and　SR,　which　is　the　weak　component　of　the　joint.　Conductivity　is　an　important　factor　affecting　the　tangential　electric　field　in　XLPE/SR　interface　of　HVDC　cables　by　changing　the　potential　distribution　in　the　insulation.　Considering　that　the　cable　joint　consists　of　two　kinds　of　insulation,　the　relationship　between　their　conductivity　ratio　coefficient　and　tangential　electric　field　of　interface　is　primarily　calculated.　It　is　found　that　reducing　the　difference　of　conductivity　between　XLPE　and　SR　can　keep　the　tangential　field　strength　of　the　interface　at　a　relative　low　level.　In　addition,　considering　the　nonlinear　conductivity　of　the　insulation,　the　tangential　electric　field　of　the　interface　under　DC　superposition　switching　impulse　voltage　is　calculated.　The　results　show　that　the　tangential　field　strength　of　the　interface　is　the　largest　when　DC　superposition　positive　switching　overvoltage　at　low　temperature,　which　makes　the　probability　of　discharge　and　breakdown　in　the　joint　to　be　highest.　And　maximum　tangential　field　strength　of　the　interface　is　larger　under　DC　superimposed　both　positive　and　negative　switching　impulse　voltage　than　that　of　the　steady-state　at　higher　temperature.　©　2020　IEEE.