Abstract: As a transition metal, titanium is extremely sensitive to hydrogen, and a trace amount of hydrogen may lead to hydrogen embrittlement in titanium alloys, which in turn affects their service performance as liquid hydrogen storage tanks,welded load-bearing frames, aircraft fuselages and aerospace fasteners. The diffusion and dissolution behaviors of hydrogen in titanium alloys were briefly described, the sources of hydrogen in titanium alloys for aerospace applications were analyzed.The mechanisms of hydrogen in three types of titanium alloys（α-Ti, β-Ti, and（α+β）-Ti） were focused on based on the four commonly used theories, namely, hydrogen-enhanced debonding, hydrogen-induced local plasticity, stress-induced hydride cracking and adsorption-induced dislocation launching, and the main factors affecting hydrogen embrittlement of titanium alloys such as temperature, stress, etc were outlined. Finally, the protective measures to improve the hydrogen resistance of titanium alloys were reviewed from the aspects of heat treatment, component design, structural optimization, surface strengthening and coating layer, etc., which can provide the theoretical basis for the selection of titanium alloys for components or equipment in the aerospace and energy fields and the effective prevention of hydrogen embrittlement.