Abstract: To clarify the influence mechanism of Vicat softening temperature (VST) of low smoke zero halogen (LSZH) flame-retardant materials on the extrusion process, and to solve the extrusion quality anomalies of LSZH-1 material on the HT-12 production line, an actual production case was taken as the research object. Comparative tests were designed to identify the root causes from three dimensions: material, process and equipment; targeted optimization strategies were proposed and verified in production. It is found that the VST of LSZH-1 material is only 84.4 °C due to its formulation system. Combined with the excessively high temperature in the feeding section and the weak pressure-building capacity of the low-pressure screw of the HT-12 line, this induces plastic bridging in the barrel, resulting in reduced outer diameter of the product and large fluctuations in barrel pressure and main motor current. By replacing with a high-pressure flame-retardant screw and optimizing the drying and feeding section temperatures, the fluctuation of extrusion pressure is controlled within ±0.3 MPa, current fluctuation within ±1.5 A, and outer diameter deviation within ±0.3 mm, achieving continuous and stable production. This paper reveals the correlation between VST and extrusion stability of LSZH materials: the lower the VST, the easier premature softening and bridging occur, requiring temperature adjustment and stable barrel pressure; materials with higher VST exhibit better process adaptability and stronger extrusion stability.