The transmit chain with stable performance is one of the key devices of the radio frequency identification (RFID) based on SAW.A transmit chain structure of SAW reader has been designed by improving the typical transmit chain structure.The improved structure is based on the principle of zero IF modulation.The modulation of transmitted signal,the isolation of transmitted and received signals are realized by RF switch.This improved structure excludes the upconverter circuit and the circulator, simplifying the circuit and reducing the interference. The important components of the transmit chain such as local oscillator,power amplifier and RF switch are researched.The design and fabrication of the circuit modules are completed,and the design requirements are verified by experiments.