Titanium alloy has excellent specific strength and corrosion resistance, so it has a wide range of applications in weapons and aviation industry. The metastable β titanium alloy has the highest specific strength because the second phase precipitation can be strengthened by heat treatment. In the field of armor, materials will be affected by high-speed impact, so the study of mechanical behavior of materials under high strain rate is indispensable. When applied in the field of armor, materials will be affected by high-speed impact. The strain rate of materials is very high, and its mechanical behavior is different from usual. Therefore, it is indispensable to study the mechanical behavior of materials under high strain rate. For titanium alloy, the morphology and content of α phase have a great influence on its mechanical properties. In recent years, many scholars have studied the effect of α phase on the mechanical properties of titanium alloys. In metastable β-Ti alloy, the content of α phase not only affects the strengthening effect of the second phase, but also changes the content of β-phase stable elements in the matrix β-phase, which changes the deformation mechanism of the alloy. The effect of α phase on the relative mechanical properties of α+β titanium alloys such as TC4 has been studied in detail, but less research has been done on metastable β titanium alloys. Therefore, in this paper, the effect of α phase on the dynamic mechanical properties of metastable β titanium alloys was studied by adjusting the morphology and content of α phase in titanium alloys by heat treatment. The experimental alloy was a high strength and low cost metastable β-titanium alloy 2A2F(Ti-2Al-9.2Mo-2Fe-0.1B) jointly developed by Korea Institute of Materials Science and Beijing General Research Institute for Nonferrous Metals. After heat treatment, a cylindrical sample of Ф4 mm×4 mm was selected along the axial direction of the rod by wire cutting with electric spark. The samples were tested with separated Hopkinson pressure bars, and the obtained strain-time and strain-rate-time curves were analyzed to obtain the true stress-strain curves. Critical strain rate under the dynamic flow stress, plastic strain and shock absorption, dynamic mechanical performance index as measure material using optical microscope (OM) and scanning electron microscopy (SEM) to organize observation, using SEM matching spectrometer on organizational elements for statistical quality score, using electron back scattering diffraction analysis of the load of the organization. The size of β-grains was basically the same after solution treatment under three phase transition points. After solution treatment at 650 ℃, there were needle-like primary α phases distributed on the grain boundary and inner-grain of β phase. Compared with the treatment at 650 ℃, the primary α phase was partially dissolved after the treatment at 760 ℃, and the primary α phase was significantly reduced, mainly consisting of primary α phase at grain boundaries and strips along grain boundaries. The aspect ratio of primary α phase also decreased. After solution at 790 ℃, the primary α phase of the microstructure was dissolved in large amount. The α phase consisted of primary α phase at grain boundary, short rod-shaped and spherical primary α phase. In terms of dynamic flow stress, 2A2F treated at 650 ℃/30 min/WQ was the highest, which was about 17% higher than that treated at 760 ℃/30 min/WQ. In terms of plasticity, 2A2F treated at 760 ℃/30 min/WQ was about 31% higher than that treated at 650 ℃/30 min/WQ. With the increase of heat treatment temperature, the dynamic flow stress decreased and the uniform plastic strain increased. The dynamic flow stress of 2A2F treated at 650 ℃/30 min/WQ was higher than that of 2A2F treated at the other two heat treatment systems. This was because when the size of the second phase was small, the fine dispersion primary α phase of hcp structure would hinder the dislocation movement and increase the strength of the material. By metallographic quantitative analysis, the content of α phase at 650 ℃/30 min/WQ was about 35%, that at 760 ℃/30 min/water-quenching (WQ) was 34%, and that at 790 ℃/30 min/WQ was 16%. The higher the content of α phase, the better the strengthening effect of the second phase, the higher the dynamic rheological strength and the worse the ductility. After solution at 650 and 760 ℃, the dynamic flow stress of the samples did not increase significantly after yield. After solution at 790 ℃, the samples still showed a slight increase after yield, and the plasticity of the samples was significantly stronger than the first two. After EBSD test, it was found that the plasticity of the sample increased after solid solution at 790 ℃ after the yield point due to the appearance of ｛332｝<113> twins. In this paper, it was found that when the solution temperature of 2A2F was between 650 and 790 ℃, with the increase of the solution temperature, the content of primary α phase in 2A2F decreased, the width of primary α phase increased, and it tended to be spheroidization, the dynamic flow stress decreased, and the uniform plastic strain increased. Twin deformation appeared in the microstructure after heat treatment at 790℃/30 min/WQ during the loading process. After EBSD analysis, it was found that the mechanical twins were ｛332｝<113>. Due to the twinning deformation, the dynamic flow stress still increased in the plastic stage, and the uniform plastic strain also increased significantly. It was significantly better than 650 ℃/30 min/WQ and 760 ℃/30 min/WQ. © Editorial Office of Chinese Journal of Rare Metals. 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