The Johnson-Cook model and the gradient-dependent plasticity were used to investigate the width of adiabatic shear band (ASB) and the strain rate effect of Ti-6Al-4V. The ASB width was defined as the width (w5%) of the region surrounding the band center over which the temperature differed from its peak value by less than 5%, similar to the viewpoint proposed by Batra and Kim. The theoretical results show that the calculated ASB widths are closer to the lower bound (12 μm) and upper bound (55μm) measured in experiments when the nominal strain rate is in the range of 800 s-1 and 1400 s-1 if the total ASB widths are 0.3235 mm and 0.0705 mm, respectively. At lower strain rates, the ASB is wider. As the strain rate increases, the ASB width rapidly decreases. However, at higher strain rates, the ASB width approaches constant. The present theoretical result is similar to the analytical result by Dodd and Bai and very consistent with the experimental result of tungsten alloy by Weerasooriya and Beaulieu, and is similar to the former part of the numerical result by Klepaczko and Rezaig