Since RFID technology is developed, 13.56 MHz RFID system with its excellent performance is widely applied. 13.56MHz RFID system is a passive system. So the performance of the antenna directly affects the performance of the RFID system. The paper simply introduces the basic principle of 13.56MHz RFID system antenna. And by using HFSS, the paper can get some circuit parameters of the antenna, including the equivalent inductance, loss resistance and so on. Moreover, the paper analyze the relationship between the equivalent inductance and the wire width of the antenna and trace spacing. And the paper introduce the design and simulation of matching circuit.