Cyclic deformation behavior and micromechanisms in strain controlled low cycle fatigue of a near β-Ti alloy Ti-3Zr-2Sn-3Mo-25Nb (TLM) with the different microstructures, which are solution treatment and aging treatment conditions, were comparatively investigated at room temperature. The results showed that the cyclic hardening/softening behavior of TLM alloy was significantly correlated with strain amplitude and microstructure.SThe low cycle fatigue life of the alloy at the solution treatment was higher, and the elastic modulus increased from constant to sharp with the increase of cycle number and total strain amplitude, while the elastic modulus of the aged alloy had a little change during the cycle deformation.SThe microstructure characteristics showed that deformation mechanism of the solid solution alloy was mainly dependent on the formation and their interaction of dislocation slip, the deformation-induced α martensites and the unique "Z" type β twin, while the aging alloy was mainly dependent on dislocation slip.