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. Flame retardant properties of unprotected cable, cable fireproof coating, as well as fireproof sheath, coated cable cladding material, and inorganic intumescent layer composite material and other fire protection measures were compared. For 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 fire resistance test, due to the thermal insulation protection provided by inorganic intumescent layer composite material, the fire-resistant time of composite cables reached 15290 s, which was 2.6 times that of cables with fireproof coating and 2.2 times that of coated fire-resistant cables, achieving fire-resistant retrofitting of existing cables.