In this paper, A micro-mechanics finite element model is established based on the realistic microstructure of Ti-6Al-4V alloy. And considering the dual-phase characteristic, the micro deformation behaviors during the uniaxial tension at ambient temperature are studied. The results show that the hard transformed β matrix (β_t) in Ti-6Al-4V alloy bears most external loading force, while the external load deformation is mainly carried out by the soft primary α phase (α_p). The strain and stress distribution in different regions within the same phase are also strongly asymmetrical. With the increase of the macro-strain, the strain ratio of α_p to β_t and the stress ratio of β_t to α_p are basically unchanged at first, then increase rapidly, and finally maintain stability. The volume fraction and grain size of α_p have a significant effect on the strain and stress distribution in the constituent phases. With the increases of volume fraction or the decreases of grain size, the strain ratio and the stress ratio increases and decreases, respectively.