The quasi-static and dynamic stress-strain curves of TC2 Ti-alloy were measured by means of electronic universal testing machine and split Hopkinson pressure bar (SHPB) respectively, and the dynamic flow stress characteristics at high strain rates were investigated, meanwhile, the relevant microstructure evolution of the alloy was examined. The results show that the strain induced effect of strengthening and plasticizing for TC2 Ti-alloy is sensitive to strain rates obviously in the range of 1100- 6000 s^-1, but the two effects were weakened for the strain rate above 4800 s^-1. An adiabatic shear line at an angle of about 45° from the loading direction was observed in the samples by strain rate of 2500 s^-1, and a shear bands may appear as the strain rate further increases, however which were not significantly widened due to the presence of the blocking zone, resulted from the slippage and agglomeration of the dispersed β particulates. The Johnson-Cook constitutive model was modified with the term of adiabatic temperature rise, then a new model was built by means of non-linear fitting. By comparison of prediction data with experimental data, it follows that the average relative error and the correlation coefficient are 2.18% and of 0.9935 respectively for the above two group data. As a result of the foregoing, the rheological behavior of TC2 Ti-alloy by high strain rate at room temperature can be described well with this improved model.