Based on finite element analysis, we propose a simulation model for radio frequency identification (RFID) SAW tag devices. Electric properties of metal electrode on substrate greatly affect the characteristics of the device and are discussed in the paper. Then the right and left boundary conditions for the device are applied to remove large unwanted waves generated by wave propagation near the boundaries. To save computation time, a 2-D model is proposed, where some mesh skills are applied. The tag device is simulated in 2 steps. First, we use modal analysis to get the device phase velocity and harmonic frequency. Second, a tag with multireflectors is simulated. Based on the simulations, we have designed and fabricated a SAW tag. A comparison is made between simulation and experimental results and shows our simulation model agrees with the experiment very well.