Abstract: In response to the demand for rapid fire-resistant upgrading of in-service cables, a coated cable cladding material and an inorganic intumescent layer composite were successfully developed, which improved the fire resistance of cables. The flame retardant properties of a fireproof sheath, the coated cable cladding material, and the inorganic intumescent layer composite were compared and studied. The fire resistance performance of cables wrapped with the cable substrate, cable fireproof coating, and the above three cladding materials was evaluated. For the inorganic intumescent layer composite, the smoke density rating was 0.4, the peak heat release rate was 5.8 kW·m^–2, the peak smoke release rate was 0.002 m²·s^–1, and the combustion growth rate index value was 0.58 W·s^–1. In the fire resistance test, due to the thermal insulation protection provided by the inorganic intumescent layer composite, the fire-resistant time of the composite cable reached 15290 s, which was 2.6 times that of the cable with fireproof coating and 2.2 times that of the coated fire-resistant cable, thereby achieving fire-resistant retrofitting of existing cables.