In the present article, the effects of Al, Zn, Fe, Ni, and Cu powders on the thermal degradation of waste polystyrene were studied. The results show that the catalytic effects of metal powders have a relationship with their activities. The catalytic effects increase with the increasing activities of metals. It is suggested that polystyrene degrades through a transient intermediate in the presence of metal powders, and the degradation of the transient intermediate is the rate-determining step.