For the transmission pressure 27.5 kV of the railroad AC contact network, and the nonparallel (on earth) arbitrary plane for the wire wearing surface, the optic fiber was used to isolate the high voltage and to transmit the measurement signal. A remote gratingtype adaptive automatic machinery transducer was used to detect the AC contact network wire wearing surface with about seven meters from the ground. Based on this method, a system was designed and calibrated, achieving measurement of wire rubbing with highvoltage. The actual measurements indicate that the method and the system satisfy the demand of the measurement of contact network wire wearing. The method is significant to the geometric sense measurement of the high voltage charged body.