Abstract: In view of the problems that sensor frequency signal transmission exists false positive and off line, the paper designed high-precision frequency-current conversion circuit based on single-chip input capture, and presented five parts of the hardware circuit in detail, including the single-chip circuit, power supply circuit, voltage matching circuit, D/A conversion circuit, voltage and current conversion. The 200 ~ 1 000 Hz frequency signal can accurately converted to 4~20 mA standard current signal by the circuit with high accuracy, good stability.