In the present work, Al2O3 was coated on the quartz fiber by the sol-gel method to improve the high temperature mechanical properties of the quartz fiber/methyl silicon resin composites. The X-ray diffraction results showed that the crystalline property of the Al2O3 coating increased with the processing temperature. Before 500oC treated, the Al2O3 coated fiber reinforced composites have lower flexural strength than the commercial fiber reinforced one. While after 500oC treated, the flexural strength of Al2O3 coated fiber reinforced composites was higher than the uncoated reinforced one. And the flexural strength for the 400oC treated Al2O3 coated fiber reinforced composites was higher than that of the 600oC treated one. The mechanism of the crack propagation in the purchased and Al2O3 coated fiber reinforced composites was also studied through scanning electronic microscopy (SEM).