Abstract: The effect s of volume f raction of alumina silicate short fibers in crystal and their length on micro yieldbehaviors of Al₂O₃-SiO₂ ( sf) / Al₂Si metal mat rix composites (MMCs) fabricated with squeezing cast were investigated by continuous loading on an Inst ron5569 tester with measuring installation of accuracy 10 - 7 . It is shown that themicro yield st rength of the MMCs decreases while the macro yield st rength and Youngps modulus increase when thevolume f raction of alumina silicate short fibers increases and the micro yield strength of the MMCs decreases whilethe macro yield st rength increases when the length of the short fibers in crystal increases.