The effects of heat treatment on transformation behavior, properties and thermo-mechanical cycling fatigue of Ti49.8Ni50.2 alloy wire were investigated. With increasing of annealing temperature, R→B19′ transformation temperatures increase, while B2→R transformation temperatures decrease. The two transformations temperatures will overlap upon annealing at 823 K. Recovery occurs in the specimen annealed below 823 K, σM decreases slightly with the increase of annealing temperature, The specimen annealed at 723 K shows the largest stable recovery strain while its upon annealing above 823 K, the recrystallization of the specimen will occur, its σM and stable recovery strain decrease sharply, while its fatigue life increases from 103 to 104 magnitudes