The wear behaviors of polytetrafluoroethylene (PTFE), graphite-PTFE, and MoS2-PTFE composites with volume content of filler from 0 to 50% were evaluated against a steel ball using an SRV wear tester under a severe wear condition (both at high speed and high load) and the wear debris produced during the friction process were clearly observed by scanning electron microscopy (SEM). Results indicate that the wear debris produced during severe friction tests are in the form of complete unbroken wavelike ribbons for the good ductility polymer-based composites, or in a form of flake for the poor ductility polymer-based composites. Based on the experimental results of the wear debris formation during the severe friction process, a wear model about extrusion wear of the polymer-based composites in the contacting region is proposed. From the mechanism of friction extrusion proposed in this article, the phenomenon that the wear debris is a multilayer and oriented film can be well explained.