Insulated polyimide (PI) composites filled with short glass fibers (SGF), polytetrafluoroethylene (PTFE), SiO₂, and polyphenylene (PPL) are specially designed, prepared, and the tribological properties are systematically investigated with references to the special requirements for frictional materials used in ultrasonic motors. The hardness and thermal decomposition temperature of the insulated PI composites are comparable to that of conductive PI composites. However, these insulated materials present excellent friction and wear performance, especially under high loads and speeds. Scanning electron microscopy (SEM) analysis of the worn surface indicates that adhesive and fatigue wear dominate the wear mechanisms.