摘要： Microstructures of quartz in Honghe mylonite zone are studied and recent result of microstructural paleopiezometry is used in this paper to estimate the differential flow stress and strain rate for the southern Honghe fault zone. The calculations show that the differential flow stress during the development of mylonites of the southern Honghe fault zone varied gradually from 45MPa in the south to 120MPa in the north. Because the formation depth of mylonite zone became shallow from south to north, this variation indicates the decrease of flow stress with depth. The strain rate was roughly of the order of 10-12/se