A real-time disc-cutter wear monitoring system of shield machine based on eddy-current sensor is established so as to control the wear and working status of disc-cutter. The distance variations between disc-cutter ring and sensor are turned into electrical signal and then based on which the wear of disc-cutter ring can be calculated. The detection mechanism of eddy-current sensor is discussed emphatically. The non-contact eddy-current sensor with compact structure and high detecting accuracy is designed. Th...