Surface preparation is potentially important to the mechanical and biomedical properties of NiTi shape memory alloys. In this paper, the effect of surface preparation on fatigue life of a Ti-55.2wt%Ni alloy has been studied. Surface of the NiTi wires is prepared by five methods of chemical etching, electropolishing, oxidizing, mechanical polishing A and mechanical polishing B, and then examined by the self-developed fatigue evaluation device. Under scanning electron microscopy (SEM) the fractures of all specimens show dimple morphology. It is found that compared with the samples after chemical treatment, mechanical polishings and thermal oxidation, electropolished sample has longer fatigue life for its lower surface roughness despite a lack of face-hardened layer.