A 2-D nonlinear thermo-mechanical coupled finite element model was developed. Numerical simulation of vacuum hot bulge forming process of titanium alloy cylindrical workpiece was carried out using the FE software MSC.Mrac. The temperature field and displacement field of vacuum hot bulge forming process of titanium alloy cylindrical workpiece were calculated using the model. The corresponding experiments were carried out. The simulated results are in good agreement with the experimental results, The wall thickness effects of the cylindrical workpiece were simulated numerically using the developed model. The relationships between bending angle of cylindrical workpiece and wall thickness, between maximum bulge height and wall thickness and between residual stress and wall thickness were discussed under certain technical conditions during the vacuum hot bulge forming process. The results will lay a theoretic foundation for optimizing technical parameters of vacuum hot bulge forming of titanium alloy in future manufacturing process.