In this study, quartz fibers were heated at 600 degrees C, 700 degrees C, 800 degrees C and 900 degrees C for 10 h respectively. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and fiber tensile test were employed to examine the surface morphology, structure and tensile strength of quartz fibers. The SEM images indicated that when fibers were heated up to 600 degrees C, dot flaws appeared on fiber surface and when the temperature reached 700 degrees C, new strip flaws appeared on the fiber surface. HR-TEM images showed that when fibers were heated up to 700 degrees C, some ordered regions (nanometers) appeared on the fiber surface. Furthermore, the nanometer crystallites were found on fiber surface when fibers were heated at 900 degrees C. The defects on fiber surface, according to fiber tensile test, had a significant effect on mechanical property of quartz fibers and caused drastic reduction in fiber tensile strength. It is considered that the mismatch between the ordered regions and amorphous regions induced new defects on fiber surface, which led to further decrease of fiber tensile strength. (C) 2012 Elsevier B.V. All rights reserved.