Abstract: To improve the quality of the output signal and the reliability of the frequency shift track circuit code sending device, this paper designed a code sending device based on a Direct Digital Synthesizer (DDS) chip. The working principle of this device was that the microcontroller directly controlled the DDS chip to generate a frequency shift signal, which was amplified and filtered by the later stage circuit, and output to the testing loop for the vehicle antenna to receive; the microcontroller provided an RS-485 communication circuit to receive control data from the upper computer, and organic light emitting diode display screens, and buttons which served as the operator interface for portable devices. Through testing and verification, the device can accurately output frequency shift keying modulation signals of ZPW-2000 and FTGS frequency shift track circuits, improve the resolution and accuracy of the output signal, thereby reduce interference between adjacent track sections and facilitate demodulation of locomotive signal equipment. Compared with existing frequency shift track circuit code sending devices, this device has the advantages of high signal quality, simple structure, high reliability, and convenient operation.