When the shape memory alloy(SMA) completely consists of austenite phase that shows the super-elastic property, if the external energies, such as stress, crack, propagation and lamination, etc. are increased in this alloy until the austenite phase was transformed into the martensite phase, they are enough to change the mean free path of electrons correlated with the electrical resistivity of materials in the microscopic point of view. On the basis of the above concept, we carried out the feasible study for SMA wire as a strain sensor using the super-elastic property of SMA. The SMA wires of diameter 41 ㎛ were utilized for a sensor material. The relationship between electrical resistivity and tensile properties of the Ni-Ti based SMA wires during tensile loading was investigated. Since the strain is very sensitive to the minute change of electrical resistance of SMA wire, it is possible to use the SMA wire as a sensor of such physical quantities. In the study, the possibility for the application of Ni-Ti SMA wire as a sensor was investigated. The sensing system was able to measure the strain up to 6 % with 0.22 % measuring error. The sensitivity described by the ratio of electrical resistivity showed 0.00005.