The　middle　joint　is　one　of　the　serious　links　of　temperature　rise　of　cable.　For　studying　whether　the　use　of　explosion-proof　box　will　further　aggravate　the　temperature　rise　of　the　middle　joint　and　in　view　of　the　10　kV　three-core　cable　middle　joint　which　is　widely　used　in　urban　power　supply　and　distribution　system，a　three-dimensional　multi-physical　field　simulation　model　is　set　up　by　using　finite　element　method.The　influence　process　of　the　explosion-proof　box　on　temperature　rise　of　the　joint，the　law　of　temperature　rise　of　joint　under　different　volume　of　explosion-proof　box　and　the　cooling　effect　of　filling　quartz　sand　particles　on　the　joint　are　analyzed.　The　study　results　show　that　the　floating　of　the　air　due　to　heat　in　the　explosion-proof　box　causes　local　centralized　heating　of　the　cable　joint，which　will　further　aggravate　the　temperature　rise　of　the　joint.　In　case　of　sufficient　large　volume　of　the　explosion-proof　box，the　air　flow　channel　which　is　formed　inside　is　helpful　in　reducing　temperature　of　the　joint；When　quartz　sand　particles　are　filled　in　the　explosion-proof　box，the　highest　temperature　of　the　joint　is　only　55　℃，which　is　9.5　℃　lower　than　that　without　the　explosion-proof　box.The　simulation　results　are　compared　with　the　experimental　results　and　the　relative　error　is　within　±10%，which　meets　the　engineering　error　requirements.The　study　results　can　provide　reference　for　the　application　and　selection　of　explosion-proof　box　in　the　middle　joint　of　10　kV　three-core　cable.　©　2023　Xi＇an　High　Voltage　Apparatus　Research　Institute.　All　rights　reserved.