In the aerospace test, Signal source is the core component. It provides various signals what are needed by test. However signal transmission’s reflections and noise always cause interference. It will impact the accuracy of signal. Therefore, the precision, stability and reliability of signal source in space telemetry experiment are very important. This paper adopts FPGA + AD768 to achieve a precision, stability signal source. By the assessment test, this system is proved to be feasible and stable.