Abstract: The strength of samples with quartz and calcite gouges was measured at elevated temperatures and confining pressures. The strength of quartz fault zone was very sensitive to pressure up to 400℃, and its response to temperature was outstanding only at high temperature ( > 400℃). The strength of calcite fault zone was very sensitive to temperature, while the effect of pressure could only be seen when the temperature was lower than 200℃. As temperature increased, the sliding mode for both quartz and calcite fault zones changed from stick-slip to stable sliding. The transition for quartz zone took place between 400℃ and 500℃, but it took place between 200℃ and 300℃ for calcite fault zone.The microstructure of samples deformed under different condition was studied. It indicated that the deformation of quartz fault zone was controlled by cataclastic flow up to 400℃, and by intracrystallization and recrystallization when the temperature was higher than 400℃. The predominant deformation mechanism of calcite fault zone changed from cataclastic folw to intracrystal gliding, and then to syntectonic recrystallization as temperature increased from 200℃ to 600℃. The first transition took place between 200℃ and 300℃, and the second between 400℃ and 600℃. Therefore, it is clear that the difference in mechanical behavior, dis-cribed above, resulted from the difference in deformation mechanism. The stick-slip may be related to cataclastic flow for both quartz and calcite fault zones.