Abstract: The thermo-mechanical behaviors of shape memory alloy (SMA) fiber reinforced smart structure with damages were analyzed through variational principle. Mathematical expressions for meso-displacement field , stress-strain fieldof typical element with damages were presented , and a failure criterion for interface failure between SMA fibers and matrix was established. The failure criterion was geometrically characterized with an example. The results may provide atheoretical foundation for further studying on integrity of SMA smart structures.