The purpose of this study is to investigate the effect of heat treatments on the martensitc transformation and tensile deformation behavior in Ti-Ni-B alloys with various boron concentration. Three types of heat treatment are given to the specimens; i) solution treatment ii) aging iii) thereto-mechanical treatment. In solution treated specimens, R-phase transition which is related to abnormal increase of electrical resistance prior to martensitic transformation has been formed at a boron content of 0.2at% and the M, temperature has been decreased with the increasing of boron content. However, It has not been affected by aging, while that of thereto-mechanically treated specimens has been remarkably increased in the vicinity of recrystallization temperature. The thereto-mechanically treated specimen has showed a good thermal fatigue characteristics, shape memory effect and superelasticity in comparison with the solution treated specimen.