Abstract: One hundred and fifty layers of 316 L stainless steel plates were successfully joined via the vacuum diffusion bonding. The mechanical properties and interfacial microstructure of joints were studied by tensile tests and metallographic observation. The results indicated that the yield strength and tensile strength of the base material(BM) processed by the same diffusion bonding parameters decreased significantly and the elongation increased obviously. Compared with those of the processed BM, the yield strength of the joint perpendicular to the boding interface increased, and the tensile strength and elongation decreased. The yield strength of the joint parallel to the boding interface was higher than that of the BM, the tensile strength equivalent to that of the BM, and the elongation lower than that of the BM. All the tensile samples including room-temperature and elevated samples exhibited typical ductile fracture. Each zone including the top, middle and bottom of the joint showed good bonding appearance, and the interfacial microstructures at different zones were similar.