<p>High-temperature titanium alloys are continuously developed driven by the demands of aero-engines, of which the strain accumulation during the primary creep stage is critical to the long-term reliability and stability of components. Based on the Li’s energy equivalence principle, this paper develops a theoretical model for the temperature–stress-dependent primary creep strain of titanium alloys by considering the contributions of the thermal energy and primary creep dissipation energy to the transition into the steady-state creep stage, as well as the equivalence between these two energy forms. The innovation of this work lies in the theoretical quantitative characterization of the influence of temperature on the relationship between primary creep strain and steady-state creep rate. The model predictions show good consistency with acquired experimental data on the temperature–stress-dependent primary creep strain of titanium alloys. This study provides a theoretical basis for the quantitative evaluation of the primary creep behavior of titanium alloys at high temperatures.</p>