The experiments on solid-phase joining of bulk nanostructured semi-finished products out of Ti-6Al-4V alloy performed under conditions of low temperature superplasticity allowed establishing that the process of joining is of a deformation origin mainly. It has been established that under conditions of low temperature superplasticity (SP) the quality of a solid-phase joint of bulk nanostructured Ti-6Al-4V alloy parts depends on a strain value, and the strain required for processing a joint with strength and plasticity values of a basis material increases with decreasing temperature. The obtained result testifies a governing role of deformation and can be basic for developing a model of solid-phase joining under conditions of low temperature superplasticity.