The therma l oxidation of Ti-50at% Ni alloy between 300℃-400℃ offers a compact thin oxide film. This oxide film on the TiNi specimens of 0.26mm thick affects little on shape recovery ratio and shape recovery temperature. The Ni concentration in oxide film is decreased with increasing oxidation temperature. The existence of this oxide film on TiNi alloy reduces effectively both passive current density of anodic polarization and release of Ni ions in saline solution.in addition.the cell culture experiment further comfirms the advantageous influence of thermal oxidation on the biocompatibility of TiNi alloy.