<p>Using polyvinyl chloride (PVC) and acrylonitrile-styrene-acrylic resin (ASA) as raw materials, and adding three common inorganic fillers, namely muscovite, CaCO₃ and talcum powder, the mechanical and thermal properties of polymer blends are improved and their application scope is expanded. PVC/ASA blends were prepared by extrusion molding technology, and the influence mechanism of inorganic fillers on the comprehensive performance of the blends was systematically studied. Mechanical property tests show that the lamellar structure of talcum powder effectively transfers loads and significantly enhances mechanical strength. When the addition amount is 15phr, the tensile strength reaches 27&#xa0;MPa and the flexural strength reaches 45&#xa0;MPa. SEM shows that when the talcum powder content increases to above 10phr, talcum powder forms a tight interface grid with the PVC/ASA matrix, without obvious holes and de-bonding zones. This structural feature provides microscopic support for the significant improvement of flexural strength under high filling amount. Thermogravimetric analysis (TGA) indicated that talcum powder and Muscovite synergistically enhanced thermal stability through the lamellar barrier effect (with a 5% weight loss temperature raised to 281&#xa0;°C) and high-temperature resistant silicate (with a residual carbon rate of 31.5% at 800&#xa0;°C), respectively. The linear coefficient of Thermal expansion (CLTE) test shows that the dimensional stability of the talc-filled system is the best, with a CLTE of 56.2 × 10⁻⁶/℃, a decrease of 23.5%, which is attributed to the rigid constraint of its lamellar network on the expansion of the matrix.</p>