Superplastic diffusion bonding behaviors of a Ti-24Al-14Nb-3V-0.5Mo intermetallic alloy were studied at temperatures ranging from 940 to 1020 degreesC. The investigated alloy exhibits duplex (alpha (2)+ beta) microstructure with an average grain size smaller than 2 mu m. The values of the apparent activation energy in the superplastic regime were determined and the values were close to that of the apparent activation energy of the beta phase, which indicates that most of the plastic deformation was concentrated in the soft beta phase. The strain exponent and the dimensionless constant of the power law creep equation were also determined to the investigated alloy. Based on the studies, the theoretical calculations of superplastic diffusion bonding were carried out. The effects of the diffusion bonding parameters, such as surface finishes of primary sheets, diffusion bonding temperature and pressure, on the predicted bonding time were studied. The experiments of isostatic diffusion bonding were carried out and the calculated results were in agreement well with the experimental results. According to the theoretical calculations and the experimental results, the optimum diffusion bonding process of the investigated alloy was determined. The microstructural transformations during superplastic diffusion bonding process and bonding mechanism were discussed too.