Analysis the contribution of constituent phases to mechanical properties is critical to design the microstructure of titanium alloys. For this reason, the microscopic stress and strain in soft primary α (α<sub>p</sub>) and hard transformed β matrix (β<sub>t</sub>) are quantitatively analyzed by a microstructure-based finite element model to determine their contributions to the strength and ductility of Ti-6Al-2Zr-1Mo-1V alloy. The results show that microscopic stress in both α<sub>p</sub> and β<sub>t</sub> shows a normal distribution. The peak stress and stress peak height of β<sub>t</sub> are much larger than that of α<sub>p</sub>. While, α<sub>p</sub> has large peak strain and β<sub>t</sub> has large strain peak height. As α<sub>p</sub> volume fraction decreases from 49% to 12%, the contribution of β<sub>t</sub> to ultimate tensile strength (UTS) and failure strain (FS) of the alloy increases from 59% to 91% and from 36% to 75%, respectively. However, as the contribution of β<sub>t</sub> increases, UTS of the alloy increases 17% and FS decreases 21%. This finding quantitatively reveals the contribution of constituent phases to strength and ductility and provides a basis to design the microstructure of titanium alloys.