The phase transformation temperatures and its associated strains of a Ni47Ti44Nb9 alloy under different restraint stresses were studied by measuring the strain-temperature and electrical resistance-temperature curves simultaneously. The results indicated that the transformation strain increases with increasing restraint stress. When the restraint stress is higher than 160 MPa, the strain recovery is not complete because of the plastic deformation of the Nb-rich phase, and the A. and A(f) temperatures increase with increasing restraint stress more remarkably than M-s and M-f temperatures, resulting in the widening of the transformation hysteresis.