<p>In this work, equivalent-based phase diagram (EPD) of ternary Ti-[Al]_eq-[Mo]_eq based on Mo equivalents ([Mo]_eq) and Al equivalents ([Al]_eq) is proposed to efficiently and precisely predict thermodynamic properties of multicomponent Ti alloys using the calculation of phase diagrams (CALPHAD) method. Here, [Mo]_eq-type solutes include Mo, Nb, W, Ta, V, Mn, Cr, Ni, Fe, and Co, whereas [Al]_eq-type elements include Al, Sn, Zr, O, N, and C. [Mo]_eq and [Al]_eq allow convenient investigation of their effects on phase transformation, phase constituents, and phase stability in Ti alloys. Moreover, two tailored methods are developed to calculate [Mo]_eq for β and α &amp; α + β titanium alloys. The phase equilibrium relationships across temperature and equivalents for the TA, TB, and TC series Ti alloys are characterized via isothermal sections, vertical sections, and phase fractions. These predicted thermodynamic properties (α, β, α₂ phases) are validated and compared with those from the conventional CALPHAD method, including phase fractions and β transformation temperature (BTT). A higher [Mo]_eq enhances the stability of the β phase, while a higher [Al]_eq increases the tendency of brittle α₂ phase precipitation. Reduction of the multicomponent Ti alloy composition space onto a two-dimensional [Mo]_eq &amp; [Al]_eq parameter domain strengthens the application of the conventional CALPHAD method in Ti alloys, thus better resolving the complexity of Ti alloy composition design and improving understanding of phase engineering.</p> Graphical Abstract <p></p>