Influence of surface treatment to diffusion bonding before joining was analyzed during the process of magnesium alloys diffusion bonding. We processed diffusion bonding by using ZK60 rolling superplasticity magnesium alloy sheets with thickness 1.5mm and grain size 8.9$m. Joint was carried out ageing strengthening by experiment study to increase its shearing strength. Ageing strengthening performance was researched under ageing temperature 150-190 °C and the ageing time 6-48h. The results showed: diffusion bonding joints’ shearing strength had enhanced in some degrees and reached 86% of basal strength when the ageing temperature is 160 °C and the ageing time is 24h. It showed that the magnesium alloy joint’s strength could be greatly improved by ageing strengthening.