Abstract: Under high-power microwave environment, transmission of electrical signals could easily be affected by electromagnetic interference and lead to loss of transmission accuracy. In order to solve the problem, an optical fiber transmission system of analog signal under microwave drying coal environment was designed. The system is based on V/F transform, takes optical fiber as transmission channels and uses FPGA as the frequency meter, ARM as data processing controller, can effectively restrain electromagnetic interference and improve transmission accuracy. The experimental results show that the system has advantages of good anti-interference ability, far transmission distance, high stability, simple circuit structure, and transmission error of small analog signal is less than 0.1%. The system provides a good solution for analog signal transmission under complex environment.