Abstract: The Young’s modulus of Shape Memory Alloys (SMA) is temperature-dependent, and SMA has super-elastic hysteresis behavior. Recognizing this, a novel SMA smart damper is proposed and designed. In which, the number of working groups of SMA wires is determined by employing a fuzzy controller; thereby, the stiffness and damping of SMA smart damper can be determined accurately and instantaneously, and the seismic responses of the controlled structure can be reduced. A simulation model is built using the fuzzy control toolbox and the Simulink block in MATLAB, and the seismic responses of a 3-story frame structure are investigated under no control, active control and fuzzy control. Simulation results show that the amplitudes of displacement and acceleration at the first floor of the frame decreased 41% and 48% respectively by using of fuzzy control, which is comparable to active control. So the designed SMA smart damper as well as its fuzzy controller is demonstrated to be effective and reliable.