Hydrogenation behavior of Ti6Al4V alloy was investigated at different hydrogenation temperatures, holding time and hydrogen pressures. Distribution of hydrogen in titanium alloy was studied by OM. Results show that hydrogen content of Ti6Al4V alloy is controlled by hydrogenation temperature, hydrogen pressure and holding time. Hydrogen content increases first and then decreases with the increasing of hydrogenation temperature, increases linearly with the increasing of hydrogen pressure. The process of hydrogenation is a diffusion of hydrogen into titanium alloy, distribution of hydrogen becomes uniform with an increase of holding time.