The effects of cold rolling deformation on the damping behavior of Ti50Ni50 alloy were investigated systematically, and the micro-mechanism was discussed. The experiment results show that the damping capacity of deformed Martensite first decreases sharply and then keep constant with the increase of frequency at the low strain amplitude; while it is almost not affected by frequency when strain amplitude is at high level. The damping capacity of deformed martensite decreases with the increase of strain amplitude, and then almost keeps unchanged. When frequency is constant. The high damping property of deformed martensite is attributed to the movements of twin interfaces and dislocations