A substantial quantity of discarded tires has inflicted harm on the environment. Microwave pyrolysis of discarded tires emerges as an efficient and environmentally friendly method for their recycling. This research innovatively utilizes the characteristics of microwave rapid and selective heating to pyrolyze waste tires into porous graphene under the catalysis of KOH etching. Moreover, this study comprehensively investigates the dielectric characteristics and heating behavior of waste tires and different proportions of waste tire–KOH mixtures. It validates the preparation of graphene through KOH-catalyzed microwave pyrolysis of waste tires, tracking morphological and structural changes under varying temperature conditions. The results indicate that optimal dielectric performance of the material is achieved at an apparent density of 0.68 g/cm3 at room temperature. As the temperature increases, the dielectric constant gradually rises, particularly reaching a notable increase around 700 °C, and then stabilizes around 750 °C. Additionally, the study investigates the penetration depth and reflection loss of mixtures with different proportions, revealing the waste tire–KOH mass ratio of 1:2 demonstrates favorable dielectric properties. This research highlights the impressive microwave responsiveness of the waste tire–KOH mixture, Upon the addition of KOH, the mixed material exhibits an augmented dielectric constant and relative dielectric constant, supporting the viability of KOH-catalyzed microwave pyrolysis for producing porous graphene from waste tires. This method is expected to provide a new method for the valuable reuse of waste tires and a technology for large-scale, efficient and environmentally friendly production of graphene.