Aluminum ion implantation into Ti-Ni alloy was carried out to clarify the effect of the surface characteristics on the superelasticity in cyclic deformation. There was no obvious changes in superelasticity in the ion-implanted specimens. The residual stress field induced by implanted aluminum ions at the surface was considered to be insufficient to assist the stress induced martensitic deformation The results indicated that the aluminum ion implantation is effective for the bio-medical applications with its synergistic effect on inhibition of hydrogen absorption.