The interfacial shear strength of SiC fiber reinforced aluminum composite has been studied by the fragmentation test of single fiber reinforced model specimens after a number of fatigue cycles. The result shows that apparent stiffness of the testing machine is influenced by cyclic loading, which will affect the calculation of fiber strength by Clough's model. An extracting test in which fragmented fiber was extracted out by dissolving the matrix material in NaOH water solution indicated that the fiber strength did not lose via vacuum hot press treatment. This result contradicts the Clough's model. The experimental result showed that the critical length of the fiber increases a little after a few cycles of fatigue loading and thus, the interfacial shear strength decreases. The reason for this is that the thermal residual stress around the fiber developed during fabrication decreases in cyclic loading.