Abstract: The reverse martensitic transformation of 8.25% pre-strained Ti49.8Ni50.2 alloy wire constrained at different constant stresses was investigated.The results show that the reverse martensitic transformation start temperature A′s and finish temperature A′f increased linearly with the increase of constant stress,which was thought to be related with the release of elastic energy of martensite,while the reverse transformation span and martensitic transformation rate were almost not changed.On the other side,linear relationship was also discovered in the recoverable strain and residual strain versus constant stress curves.The reverse transformation in elastic restraint was analyzed and the calculation formula of recovery stress and martensitic transformation rate were deduced.