With the rapid development of global "dual-carbon" (carbon peaking and carbon neutrality), the recycling of plastic gets deeper and deeper. The study of the performance attenuation law of plastics in the recycling process has an important practical guiding role in improving the recycling effect of plastics. The repeat extrusion method was used to prepared recycled polystyrene and rice husk filled composites. The effects of thermal processing cycles on mechanical properties and processing performance, as well as their performance attenuation mechanism were investigated. The results showed that repeat thermal processing could obviously reduce the tensile strength, impact strength, vicat softening temperature, and mould shrinkage of polystyrene and rice husk filled composites during the recycling processing. There was a significant linear relationship between the retention rate of pure polystyrene and the thermal processing cycles. The tensile and impact strength of pure polystyrene decreased by 14.35% and 14.55%, respectively after four thermal processing cycles. Among which, the tensile and impact strength of rice husk filled polystyrene composite decreased the most, by 14.55% and 20.01%, respectively. The addition of rice husk could decrease the attenuation rate of comprehensive performance of composites. Repeat thermal processing could improve the melt flow index for both the pure and filled composites. Repeated thermal processing has great effects on the mechanical properties of polystyrene and its rice husk filled composites, there is a relative linear relationship between them. Antioxidant can reduce the decay rate of the mechanical properties of composites. The insights obtained from this investigation can offer valuable and theoretical references for optimization of formulas and processing parameters of such related composites.