<p>Ceramifiable polyolefin composites have a great application prospect in high temperature-resistant wires and cables. Inorganic fillers play an important role in ceramifiable property during the ceramization process. In this paper, we successfully reported the synthesis of ceramifiable composites by using silicon aluminum glass powder as an inorganic filler. The effects of silicon aluminum glass powder on the microstructure, thermal conductivity, bulk density, densification and mechanical properties were compared with wollastonite fibers and silica powder at different temperatures. The result showed that the mechanical behavior and densification of the composites were the highest when the silicon aluminum glass powder was used as the filler. Especially, the PZAH sample composed of 40% polyethylene, 20% zinc borate, 25% ammonium polyphosphate, 15% silicon aluminum glass powder shows exhibited the highest mechanical properties at 1000&#xa0;°C. At these conditions, the bulk density of composite was 2.15&#xa0;g/cm³, and flexural strength was over 19&#xa0;MPa. With the increase of temperature, the reaction of ammonium polyphosphate and zinc borate led to the formation of orthophosphate glass melt. The melt binds the fillers together and ultimately forms ceramics with excellent mechanical properties. The findings in this work provided a feasible strategy for the preparation of good thermal insulation and high flexural strength PE composites.</p>