Cyclic tensile tests on superelastic NiTi SMA wires with three diameters were carried out. The effects of the different loading conditions, namely: cyclic loading-unloading number, strain amplitude, loading frequency and ambient temperature, on the mechanical behavior described by some fundamental quantities, such as transformation stress, energy dissipation per cycle, secant stiffness, equivalent damping as well as residual strain, were examined. The temperature changes of the SMA wires due to the latent heat under different loading conditions are analyzed. The results show that with the increasing of the cyclical number, the martenside transformation start stress of all the three specimens decrease, and the energy dissipation per cycle and the secant stiffness gradually reduce, while the residual strains increase, however, all the behaviors tend to be stable after 20 cycles. Under the same condition, damping and re-centering properties of 0.5 millimeter SMA are superior to the other two, but the mechanical behaviors of 1.2 and 2.0 millimeter SMAs are basally approximate. The experimental results can provide basis for the design of SMA based energy dissipation devices.