Subcritical β solution treatment of TB17 titanium alloy was carried out at the solution temperature range from 800℃ to 835℃ and the solution time range from 0.5h to 9h, and the distribution of Al, Mo and Nb elements in the primary α phase and β matrix was studied by Electron Probe Microanalysis (EPMA). Effect of subcritical β solution on precipitation of primary α phase and secondary α phase of the alloy was investigated. . The experimental results show that primary α phase presents two typical morphologies of needle-type and lamellae-type structure, which the needle-type α phase is distributed at grain interior and lamellae-type α phase is distributed at grain boundaries. The amount of primary α phase decreases with the increasing of solution temperature. No primary α phase is observed at the solution temperature higher than 825℃. The amount of primary α phase increases with the decreasing of solution temperature. The precipitation of primary α phase will reach a steady state at the solution time higher than 2h. Al element tends to be enriched in the primary α phase, and Mo and Nb element tend to be enriched in the β matrix. The Al concentration in the center of the α phase is higher than that in the edge, while the Mo and Nb concentration in the center is lower than that in the edge. Increasing the amount of primary α phase will decrease Al concentration and increase Mo and Nb concentration in the β matrix. When the amount of primary α phase is low, the secondary α phase near primary α phase presents the morphologies of needle-type or lamellae-type structure, and a morphology of the basketweave structure for the secondary α phase far from primary α phase. When the amount of primary α phase is high, the secondary α phase presents the morphologies of needle-type or lamellae-type structure.