An examination of the effects of microstructures on the adiabatic shear banding sensitivity of Ti-6Al-4V-4Zr-Mo alloy was reported. Using the technology of split Hopkinson bar, the dynamic shearing experiments on Ti-6Al-4V-4Zr-Mo alloy with different heat treatments were conducted. The obtained microstructures are divided into the lamellar, the equiaxed and the bimodal according to heat-treatment conditions. The results indicate that the lamellar microstructure has the lowest adiabatic shear banding sensitivity, while the bimodal microstructure has the highest. In the bimodal microstructure, small cracks are found in the α/β interface located in the matrix region near the adiabatic shear band, which is considered as the main reason why the bimodal ones have the highest adiabatic shear banding sensitivity.