Abstract: In view of problems that using open-loop constant voltage to drive eddy current sensor may suffer from drive current variation with temperature drift and load change, a constant current driving circuit of eddy current sensor using linear control theory was designed. The design procedure for module circuit and application circuit based on multiple-input single-output feedback control system were introduced in details. The simulation and testing results show that the circuit not only can provide constant drive current, but also has characteristics of smaller temperature drift and stronger adaptability of load variation compared with traditional open-loop constant voltage driving circuit of eddy current sensor.