Abstract:The microstructure of as-cast V-5Cr-5Ti alloy during annealing was analyzed by XRD、OM、SEM and TEM. The results show，with increasing annealing temperature,V-5Cr-5Ti alloy secondary phase of as cast V-5Cr-5Ti alloy decompose, diffuse and aggregate. The dendritic phase made by lamellar secondary phase is turn into reunion phase made by acicular secondary phase. The shape of acicular secondary phase changes coarse- elongated - tubby over time. The lattice parameters of V-5Cr-5Ti alloy after 1100℃?h annealing is 0.30362 nm, Ti and interstitial (C, N, O etc.) are combined to form more stable secondary phase, reduce the expansion of V-5Cr-5Ti alloy lattice.There are three kinds of the secondary phase in V-5Cr-5Ti alloy after 1100℃?h annealing:1) Strip secondary phase, chemical formula can be expressed as V2(CO); 2) Acicular secondary phase, has FCC structure, the lattice parameter is 0.4193~0.4256nm; 3) Elliptical-shaped secondary phase, has FCC structure, the lattice parameter is 0.4203~0.4268nm; In the process of annealing, The dendritic phase decompose and diffuse firstly, then the alloy matrix will precipitate due to alloy element desolution and separate out the reunite phases, witch is the Characteristic of acicular secondary phase. Finally, the secondary phase is chromium-alloyed stabilized precipitations of titanium-vanadium oxycarbonitride with FCC structure, which chemical formula can be expressed as (TiV)(CON).