For TC4 titanium alloy, the experiments of high-temperature stress relaxation and reloading under three loading conditions, including uniaxial tension, shear tension and plane strain tension, were conducted sequentially at 700 ℃. The differences of stress relaxation behaviors under three conditions were analyzed, and the influences of different loading conditions under stress relaxation on mechanical behaviors were explored by finite element numerical simulation. The results demonstrate that the stress relaxation rate at the beginning stage is positively correlated with the initial stress, which can be improved by the introduction of plastic deformation. At the same initial equivalent stress, the stress relaxation rate after uniaxial tension is faster than that under shear tension or plane stress tension. After shearing deformation and high-temperature stress relaxation, the flow stress peak of TC4 titanium alloy has no obvious change, and the flow stress decreases after uniaxial tension and high-temperature stress relaxation, but increases significantly after plane strain tension and high-temperature stress relaxation. In conclusion, the elongation of TC4  titanium alloy is increased by stress relaxation, which decreases the softening of material at high temperature after shearing deformation and increases the work hardening of material after plane strain tension.