Abstract: To address the market demand for Class B₁ and low-cost power cables, a structure featuring continuous extrusion of a fire-retardant ceramicizable compound between cabled core and outer sheath was proposed, replacing the conventional complex structures that rely on high-additive oxygen-barrier compounds or multi-layer fire-resistant wrapping/armoring layers. Based on this scheme, a rated-voltage 0.6/1 kV WDZB1-YJY-0.6/1 kV 5×6 copper-core XLPE-insulated halogen-free low-smoke polyolefin-sheathed Class B₁ flame-retardant power cable was trial-produced. Bunch burning performance of the cable before and after the improvement was compared. Results showed that char height of the improved cable was only 0.34 m, which was 0.25 m lower than that of the optimal conventional structure; the maximum temperature inside combustion test chamber decreased from 62 °C to 43 °C, with a reduction of 19 °C. Meanwhile, burning duration was greatly shortened from 8.70 min to 3.72 min. Combined with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses of the ceramic material composition, it was confirmed that the main phase components of ceramicized hard shell formed by fire-retardant compound were silicates and oxides, which provided thermal insulation and oxygen-barrier functions. Structurally, the improved cable eliminated core fillers and simplified the tape wrapping structure. Extruded fire-retardant layer achieved flame retardancy and thermal insulation, while reducing material cost by 5.88% with enhanced flame-retardant performance. This paper verified the effectiveness of extruded fire-retardant compound structure in improving flame-retardant grade, suppressing flame spread, and reducing combustion temperature, providing a feasible technical path and engineering reference for developing new flame-retardant cables with both excellent fire performance and good economy.