Abstract: In the Computer-based Interlocking System, a safety output module is usually designed to guarantee the safety performance of computer-based interlocking platform. In some kinds of safety output module of the Computerbased Interlocking System, the frequency-selecting function of a continuous fixed frequency signal was used to isolate the output for controlling the power signal of safety relay. The authors designed a frequency generator based on 51series single-chip microcomputer and MAX038 signal generator chip to simulate the output of this frequency signal, and PC program based on Qt to implement the monitoring and regulation of the frequency signal. This article described the construction, hardware and software design of the generator.