The stress-strain characteristics of TiNi shape memory alloy wires after constrained thermal cycles were studied. Results showed that the loading stress-strain curves exhibit a linear elastic response followed by a stress plateau if the thermal cycle stopped upon heating or cooling in the thermal hysteresis, If the constrained thermal cycle stopped upon cooling in the forward transformation temperature span, the loading stress-strain curves exhibit just the stress plateau. Similarly, the unloading stress-strain curves exhibit a linear elastic response followed by a stress plateau if the constrained thermal cycle stopped upon cooling. If the constrained thermal cycle stopped upon heating, the unloading stress strain curves exhibit immediately a plateau.