Two types of joining specimens with and without Ni foil interlayer between 316L–SS bar have been prepared by diffusion bonding in a temperature range of 850- 1050°C, under a uniaxial pressure of 10MPa for 1hours. The relationship between the bonding parameters and the tensile strength of the joints at elevated temperature was studied. Optimized processing parameters were suggested based on the testing results. It was found that the introduction of the interlayer may reduce the room temperature strength but increase the high temperature strength. This was attributed to the transformation of Fe0.64Ni0.36 formed in bonding process into FeNi3 at high temperature.