Abstract: The research on the principle and process of crystallized alumina-silica short fiber was made in this paper in order to lmprove the properties of the amorphous fibers and the composlte materials.The reaction phenomena of flbers with Al-51 alloys were examinedby EDX,X-ray diffraction,EPMA and TEM.As a result,the crystallized alumlna-silica short fibers show hlgher hardness than amorphous alumina-silica short fiber and have remarkable stability in chemical reaction with molten metal.Increase in ultimate tensile strength at elevated temperature of the crystalllzed alumina-sillca fibers reinforced Al-Si alloy was observed.