In this paper, a TiNi shape memory alloy fiber Ni matrix composite was fabricated by an electroplating method using TiNialloy as the cathode and Ni as the anode. The constrained martensitic transformation behaviors of the TiNi alloy were studiedby differential scanning calorimeter (DSC), and the results showed that two endothermic peaks appear on the DSC heatingcurves and the reverse transformation temperatures increase with increasing prestrain levels. Moreover, comparing to the freetransformation, the temperature window of the constrained reverse transformation is widely expanded due to the influence ofrecovery stress.