The deformation behavior of pure Ti, Ti-0.2wt% O, and Ti-0.4wt% O polycrystals under high strain rate was investigated by quasi-in-situ EBSD and SEM observation. Results show that under dynamic compressive deformation of 5% strain, the twinning behavior in pure Ti is very active, the twins in most grains are activated, and multiple twin variants appear in half of the grains. However, the slip trace analysis shows that the slip systems are activated in only 50% grains. With the increase in oxygen content, the proportion of twins and the twin area ratio are decreased, and multiple slips and cross slip are activated in the meantime. XRD analysis reveals that the solute oxygen atoms cause the lattice distortion and increase the c/a ratio in α-Ti, which is beneficial to the dislocation slip. The active dislocation slip inhibits the twin nucleation, and the oxygen atoms can pin dislocations to hinder the expansion of twinning boundaries. Thus, the twinning behavior is no longer active. In addition, the dynamic yield strength of pure Ti increases by about 390 MPa for every 0.2wt% increase in oxygen content. This solution hardening phenomenon mainly originates from the lattice distortion, and it is also influenced by the pinned dislocations and the jogs resulting from multiple slips and cross slip.