Abstract: The mechanical model of SMA fiber pull-out is discussed and simplified in the paper. On the basis of one-dimensional Liang-Rogers constitutive model and Tanaka exponent model for Martensite volume fraction, with limited numerical value of interfacial friction effect considered, the functional relationships between the displacement of fiber in the pull-out zone and the external load and friction upon loading and unloading are deduced under isothermal condition. In addition, a series of relative curves are given, and the influences of interfacial friction to the mechanical properties of SMA fiber are obtained. The good agreement of the results from cosine and exponent models indicates that the varying axial force model is reasonable to some extent.