Abstract: The interfacial shear strength of SiC fiber reinforced aluminum composite treated with SiC₂ was studied by the method of fragmentation and acoustic emission after a certain cycle fatigue loading. The result shows that the pretreatment with fatigue and without fatigue displays a great influence on the stiffness of the test machine which will affect the calculations of fiber strength in composite. The measurement of fiber strength of hot pressed specimens by a dissolving method indicates that the fiber strength does not lose via composite process. The critical length of fiber increases a little after certain cycles of fatigue loading and thus, interfacial shear strength decreases.