Ti-5A1-5Mo-5V-3Cr-1Zr near β titanium alloy containing the initial acicular α was hot compressed at 750~775 ℃ and 10-3~10_-1 s_-1, in which the fragmentation behavior of acicular α was investigated. With the increasing of strain, the acicular α undergoes the rotation displacement, partial fragmentation up to transform to the equiaxial morphology completely. During the fragmentation of acicular α, when the Burgers orientation relationship exists between neighbor α and β phases, the dislocations in β matrix are easy to enter into the neighbor acicular α through slip transmission at α/β interface, followed by the formation of high-density dislocations and then transforming to the sub-microstructures in acicular α. In case of no Burgers orientation relationship between neighbor α and β phases, the dislocations pile up at some α/β interface with the large orientation discrepancy. The as-resulted local stress concentration causes the formation of sub-microstructures composing of local shear bands in acicular α. Sequentially, β matrix hedges into the acicular α along the interfaces among sub-microstructures, leading to the fragmentation of acicular α. The increasing of temperature promotes the dynamic β recovery and then decreases the dislocation density, which doesn’t benefit the formation of sub-microstructures in acicular α. The increasing of strain rate decreases the deformation time, which suggests that the formation of high-density dislocations and then transformation to the sub-microstructures may not perform sufficiently in acicular α. As a result, the increasing of temperature and strain rate both delay the fragmentation of acicular α.