In order to study the effect of V element on Ti alloy, the structure and the elastic modulus of Ti-V alloy in hcp phase was calculated by the first principles pseudopotentials and the plane wave energy band method. The results show that the content of V less 5.6 at. %, theTi-V alloy have steady HCP structure, and with the increasing of the content of V, the body elastic modulus, shear modulus and young"s modulus of Ti-V alloy decrease monotonously, while the poisson ratio increase.