During the thermal treatments of α+β titanium alloys in (α+β) phase field, alloying element partitioning effect takes place accompanying with the α?β transformation, which results in the segregation of α stabilizing elements (Al, O) and β stabilizing elements (V, Mo, etc.) into the corresponding phases respectively. The element partitioning effect will further affect the microstructure characteristics (phase constitution, microstructure size), plastic deformation modes and the final mechanical properties of the alloy. In this work, the influences of solution temperature and cooling rate on the element partitioning behavior during solution process of Ti-6Al-4V alloy in (α+β) phase field were investigated. The element concentrations in primary α phase (α_p) and β transformed region (β_t) were characterized by EPMA technique. The microstructural variation of β_t with respect to solution temperature was analyzed. It was found that β_t showed an obvious increase of Al content and decrease of V content with the increasing of solution temperature, while the α_p exhibited less noticeable change, which led to the reduction of concentration difference between the two phases. Under the same solution temperature, the microstructures and element distributions at different cooling rates (water quenching, air cooling, furnace cooling) were exhibited. The slow cooling processing especially furnace cooling would induce higher volume fraction of α_p phase and more pronounced element partitioning. The microstructural characteristics of β_t cooled from different solution temperatures were further analyzed. During the water or air cooling process, the transformations of β→matensite/α_s happened, and the sizes of martensite or α_s were postulated to be dependent on the element concentration of β phase. The properties of local microstructure (α_p, β_t) were further measured by nanoindentation. It indicates that the intrinsically anisotropic character of the hexagonal crystal structure (hcp) of the α_p phase has decisive consequences for the properties, while the elastic modulus and hardness of β_t calculated by nanoindentation are mainly dominated by the width of α_s lamellas. On the basis of the above results, the relationship between solution temperature, element concentration of local microstructure, microstructure size and mechanical properties of local microstructure was finally discussed.