The correlation between the wear behaviors of graphite-polytetrafluoroethylene (PTFE) composites and their macro- and microscopic structural changes was studied in a wide graphite volume content range of 0 to 50%. It was found that the macroscopic structure of graphite-PTFE composites changes from the state of PTFE-wrap-graphite to the state of detachment between PTFE and graphite powder along with an increase of graphite volume content. The sudden change occurred at the point of graphite volume content of about 40%. In this article the positron annihilation lifetime spectrum was used to detect the properties of microscopic imperfections. The results indicated that the changes of microimperfects of graphite-PTFE composites in size and in concentration are also related to the increase of graphite volume content while the crystallinity of PTFE shows a tendency to increase. The wear behaviors of graphite-PTFE composites corresponded to the physical properties of imperfects in a macro- and microscopic sense and were reflected fairly well by the interfacial properties between crystal and amorphous regions in PTFE. The positron annihilation technique is a useful tool for the study of tribological behaviors of polymers.