In this paper, we investigated the properties of volume reduction ingot for the recycling of flame-resistant expanded polystyrene (EPS) waste. The experimental method consisted of a composite process involving EPS reduction, grinding, crushing, and degreasing. Through our study we determined that the optimum process for achieving the desired results involved a combination of multi-grinding and degreasing methods. Furthermore, we identified the optimal heat condition for the degreasing process to maintain flame retardant properties as 600℃ for a duration of 2 h. In addition, we provide evidence to support the feasibility of using this process in EPS recycling for flame retardant materials.