The static and dynamic compression tests of Ti-811 alloy with acicular microstructure have been conducted by using the Instron testing machine and the split Hopkinson bar system respectively. Its deformation and fracture mechanism under various strain rates have been studied. The results show that: the yield strength of acicular microstructure exhibits positive-negative-positive strain rate sensitivity successively with increasing strain rate. The intrinsic reason is the competition between dislocation slip and twinning mechanism. The fracture mechanisms of acicular microstructure under static and dynamic compression are obviously different, which show double-shearing and single-shearing fracture mode respectively. Saw-tooth chips formed at the end faces of dynamic compression specimen, which is due to restraint of the severe relative slide of the material at the two sides of primary shearing band by incident bar and transmission bar.