The phase transformation and mechanical behaviors of cold-rolled NiTi shape memory alloys ultra-thin sheet with 100μm in thickness are investigated. The transformation behaviors of the NiTi sheet are found to be remarkably influenced by heat treatment using electric resistance vs. temperature measurements. The martensitic transformation temperature reduced by annealing at 400°C or 600°C, and R-phase transformation appears when annealing at 400°C. The martensitic reorientation occurs when the NiTi sheets annealed at 400°C is deformed at room temperature and the maximum shape memory strain is 3.5% at 100% recovery ratio. For the NiTi sheets annealed at 600°C, a superelastic strain of 5% and a transformation stress about 500MPa are achieved.