Abstract: Double-loop mirror symmetric principle is based on electric metamaterials. We design a metamaterial structure of ancient Chinese coins with this principle. Simulation shows that the metamaterial has the characteristics of zero refractive index and can focus the electromagnetic wave to one direction. Further, we arrange the unit cells of the metamaterial to a 3×5 array and load the array to the UHF-RFID reader antenna. Then the return loss，directivity pattern and the parameter scanning curve of the gain are given in this paper. The simulation shows that the gain of the antenna with the metamaterial improves from 10.6dBi to 12.5dBi which prove the feasibility of the design.