Abstract: The elastic modulus of Ni-Ti alloys,which are with the pseudo elasticity,has been investigated by means of static tension method and nano-indentation method. The results showed that elastic modulus varied with the phase constitution of the alloy,with the elastic modulus of the matrix phase to be 24.5 GPa and the martensite phase to be 11.6 GPa. Multiple tensions lowed down the elastic modulus of the alloy and exhibited a non-linear relationship with strain. The elastic modulus determined by nano-indentation was different with that by the static tension,which is due to the ignorance of the pseudo elastic deformation in the nano-indentation.