A series of bifunctional catalysts (Fe-Ni/SiC) with microwave absorption and catalytic abilities were constructed to realize high-value application of waste plastics by microwave catalytic pyrolysis. The bifunctional performances and mechanisms were explored by a new microwave thermogravimetric oven. The bifunctional catalysts had good pore structure and the active components of Fe₂O₃, NiO, and NiFe₂O₄, which made the catalysts with good dielectric and catalytic performances. After catalysis, the heating rates and weight loss rates of low-density polyethylene were 68.18–73.39 °C·min⁻¹ and 0.59–0.68 g·min⁻¹, respectively. The increase in heating rate helped to promote the pyrolysis degree, advance the pyrolysis endpoint, and reduce the energy consumption (11.54 MJ/kg at most). When the catalyst was Fe-Ni/SiC (2:1), the highest gas yield (73.61 wt%) and H₂ content (73.89 vol%) was obtained. Moreover, the higher graphitization degree of carbon nanotubes was obtained with more Fe loading. The oriented production of high-value products could be realized by adjusting the type and proportion of active components in the catalyst.