A　cable　fire　in　a　utility　tunnel　can　cause　severe　damage　to　the　electric　power　supply　in　cities.　This　study　aims　to　understand　the　combustion　and　flame　spread　characteristics　of　cable　fires,　which　are　mainly　caused　by　overheating　from　the　excessive　current　at　the　interconnections　of　the　cables　under　spontaneous　combustion.　Fire　experiments　were　conducted　in　a　1:6　scale　model　of　a　utility　tunnel　to　analyse　the　flame　spread　characteristics　under　different　heat　release　rates　(HRRs),　vertical　distances,　and　transverse　distances.　The　findings　of　this　study　show　that　the　total　burning　time　of　the　cable　fire　increases　as　the　cable　diameter　increases,　and　the　HRR　also　shows　an　increasing　trend.　Additionally,　the　spatial　location　of　the　cable　fire　has　a　significant　impact　on　the　flame　spread.　The　terms　Hc*　and　Dc*　are　defined　to　characterize　the　flame　height　and　a　general　prediction　model　of　the　dimensionless　flame　height　influenced　by　cable　spontaneous　combustion　is　proposed.　A　dimensionless　model　is　also　established　to　describe　the　flame　spread　rate.　This　research　provides　valuable　guidance　to　aid　in　the　development　of　fire　safety　measures　in　utility　tunnels.