The steel balls surface and sub-surface defects can be non-contact detected by eddy current detecting method.The detecting signal is related to crack depth of excitation frequency and the electromagnetic characteristics of the detected steel balls.Since interference signals is in series

so it is necessary to process output signals of eddy current probe.The phase-sensitive wave detecting method is introduced in the process.After orthogonal decomposition and coordinate rotation to the output signals

the interference to defect signals can be converted to X-axis direction.Thus the interference to defect signals can be avoided.Experiments show that the detecting effect of the sensor is good.