This paper investigated the effects of different heat treatment processes (solution aging and double annealing) and pre-stretching on the microstructure and mechanical properties of Ti-6Al-4V-0.55Fe (TC4-0.55Fe) alloy with duplex microstructure and the relationship between microstructure and mechanical properties of TC4-0.55Fe alloy was analyzed. The microstructure and mechanical properties of the duplex microstructure after solution aging and double annealing were compared and it can be found that the thickness of the micron scale lamellar α phase gradually increased with the increase of aging and low temperature annealing temperature under the condition of two kinds of heat treatments, which reduced the strength and increased the plasticity of the alloy. Under the solution aging treatment, the yield strength of the samples decreases from 873MPa at 530℃ to 862MPa at 590℃ and the elongation increases by 3.2% with the increasing aging temperature. The yield strength of the double annealing heat treatment sample decreases gradually with the increase of the low temperature annealing temperature, but the elongation has been greatly improved compared with the solution aging, and the best is 23.6%.Because the strength of titanium alloy is not significantly improved by ordinary heat treatment, the plasticity of the double annealing sample is better than that of the solution aging when the aging and low temperature annealing temperature is 590 ℃, so the sample is selected to introduce the pre-stretching strengthening and pre-stretch it between the solution and low temperature annealing. After the introduction of pre-stretching, the grain deformation is obvious. And a large number of fine secondary α phase (αs) are precipitated in the precipitation-free zone (PFZ) of the alloy structure after aging strengthening. The aging after the introduction of pre-stretching can improve the yield strength of titanium alloy and only reduce a little plasticity. Among them, the sample with 1% pre-stretching deformation has the highest content of equiaxed grains, the strength is increased by 68MPa compared with that before the introduction of pre-stretching, and the elongation is only decreased by 4%, the mechanical properties are the best. According to this study, the comprehensive mechanical properties of TC4-0.55Fe titanium alloy can be improved by pre-stretching and aging strengthening after solution strengthening.