A reader antenna suitable for SAW radio frequency identification system was designed based on the basic theory of the microstrip antenna. Firstly, the basic size of the microstrip antenna was analyzed and calculated. In addition, a microstrip line with impedance conversion function was designed by using the ADS software, the input impedance of antenna was up to 50 Ω. Then the modeling and parameters optimization of the microstrip antenna were carried out by using the HFSS software, thus the final dimension of the microstrip antenna was determined. The antenna was manufactured and tested. The test results were in good agreement with the simulated ones, and the voltage standing wave ratio of the antenna was less than 2 at the resonant frequency. Finally the tag was wirelessly tested by combining with the reader, verifying the practicability of the reader antenna.