This paper proposed a complete solution of UHF RFID reader system based on S3C2440 microprocessor and AS3992 UHF Reader chip. By designing the automatic gain control(AGC) circuit and the antenna impedance automatic matching circuit, the transmit power is up to 33dBm and the receiver SNR is improved at the same time. The reader system is transplanted into the embedded Linux OS which greatly facilitates the system development and maintenance. Practice shows the RFID reader implemented in this paper has achieved high-speed identification of ISO18000-6C RFID tags and stable reading range up to 10 meters.