Abstract: To address the technical challenge of balancing flame-retardant efficiency, mechanical properties, and processability in conventional halogen-free flame-retardant polyolefin materials, a composite flame retardant based on silicate nanomaterials and a phosphazene compound was designed, and high-performance halogen-free low-smoke flame-retardant crosslinked polyolefin insulating materials and thermoplastic polyolefin sheathing materials were developed. The synergistic flame-retardant mechanism of the composite flame retardant and material preparation process were systematically investigated. Key performance indicators, including degree of crosslinking, thermal elongation, flame retardancy, light transmittance, heat release characteristics, and mechanical properties, were comparatively analyzed. Results showed that, compared with conventional single flame retardants, crosslinked polyolefin insulating material and thermoplastic polyolefin sheathing material incorporating the silicate/phosphazene composite flame retardant exhibited an increased oxygen index and significantly reduced smoke density under both flaming and non-flaming conditions, while maintaining good mechanical and processing properties. Results of finished cable tests were consistent with material test results, demonstrating that the composite flame retardant could significantly improve thermal stability and mechanical properties of materials. These findings could provide a new approach for developing high-performance environmentally friendly cable materials.