TiNi shape memory alloy was shape memory heat-treated and investigated its mechanical properties with the variation of prestrain. Also 6061Al matrix composites with TiNi shape memory allOY fiber as reinforæment have been fabricated by Permanent Mold Casting to investigate the microstructures and interface properties. Yield stress of TiNi wire was the most high in the case of before heat-treatment and then decreased as increasing heat-treatment time. ln each heat-treatment condition, the yield stress of TiNi wire was not changed with increasing the amount of prestrain. The interface bonding of Tilii/6061Al composite was fine. There was a 2μm thickness of diffusion reaction layer at the interface. We could find out that this diffusion reaction layer was made by the mutual diffusion. The diffusion rate from Al base to TiNi wIre was faster than that of reverse diffusion and the amount of the diffusion was also a littIe more than that of reverse.