Damping capacity and storage modulus of cold-rolled and annealed Ti50Ni50 SMA are systematically investigated by DSC and DMA tests. The specimens annealed at 500 oC for 1 ~ 72 h and annealed at 650 oC for short time can all reach a high tan δ value and a deep storage modulus minimum during B2→R transformation. This reveals that the occurrence of R-phase can strongly soften the storage modulus and thus promote the damping capacity of Ti50Ni50 SMA. The specimens anneaed at 650 oC for longer time have a lower tan δ value due to the diminishing of R-phase formation. Therefore, a good damping capacity associated with a significant softening storage modulus can be acquired by suitably control the annealing conditions of cold-rolled Ti50Ni50 to generate adequate of R-phase premartensite.