Abstract: The non-destructive testing probe for thickness for wave-absorbing material adopts the capacitive design. In order to improve the detection sensitivity of the probe, it is necessary to optimize the capacitive sensor. Here is given the method of electrode optimization design when two planar electrodes of the same size are detected by changing the pitch be tween the electrodes. It's concluded that the electrode spacing can not exceed the sensitive area in the course of designing, and the width of the electrode can not be too large or at the peak point. The optimized electrode structure based on the above method can obviously improve the detection sensitivity of the capacitive sensor.