In order to accurately detect the distance from the eddy current probe to the surface of the bending substrate in wide range

FEM-BEM program is used for numerical value calculation

and analysis of influence rule of different eddy current coil size

bending surface curvature size and lift-off distance on eddy current signal

so that the right size of the eddy current probe can be chosen easily.By calculating impedance signal of standard specimen and the relationship between impedance data and the lift-off distance

data fitting is carried out.Curve calibration methed can help to verify the feasibility of distance measurement of the eddy current probe in wide range.Calculation results show that this method can satisfy the engineering testing requirements.