Isothermal compression of TC4 titanium alloy with high oxygen was carried out on a Gleeble-3800 simulator over the temperature range of 990~1 030 ℃ and strain rate of 0.01~1.0 s-1, with the maximum height reduction of 60%. The hot deformation behavior was characterized based on an analysis of the stress strain behavior and microstructures. Based on the experimental data, a hyperbolic sine constitutive equation was also developed. It was found that the flow stress of the alloy increases with increasing strain rate and decreasing deformation temperature. The activation energy for deformation was 141 kJ/mol in β region. The grain size in the range of 250~255 μm and it is not sensitive to the heating temperature in the range of 990~1 030 ℃. The prior β grains become elongated in the plane perpendicular to the forging direction and dynamic recrystallization grains are observed along the grain boundaries with increasing strain rate.