The interfacial shear bond strength is a key factor determining the ultimate mechanical properties and performances of laminated metallic composites. Conventional test method is hard to accurately obtain the interfacial shear bond strength of the thin laminated metallic composites (TLMCs) because of the thin thickness and low rigidity. In this paper, an improved uniaxial tensile testing specimen to overcome the difficulty is designed by removing a portion of the cladding of the tensile specimen. The delaminated fracture strain of the cladding peeling off from the substrate can be obtained accurately during a uniaxial tensile test. The relationships among interfacial microstructures, delaminated fracture strain and the interfacial shear bond strength were studied. The research revealed that the delaminated fracture strain and the interfacial shear bond strength are all increased with increasing the thickness of interfacial diffusion layer. A formula available for calculating the shear bond strength was derived by analyzing the relationship of shear stress and delamination. As examples, the interfacial shear bond strengths of Al/Mg/Al TLMCs fabricated by different rolling reduction ratios were tested and investigated.