Abstract: It is known that the eddy current signal due to adhered material in inner wall and permeability variation has the same characteristics with that of eddy current signal of real defect during test, the two types of signals are therefore difficult to be distinguished by the conventional method. For the purpose of comparison, tests were carried out for a heat-exchange tube with real defect and for an experimental tube with artificial defect, thus to obtain the judgment method for inner wall real defect and pseudo defect. At the same time, the capability of Bobbin and MRPC probe was verified, and then the quantitative deviation of the test depth of inner wall defect and metallographic anatomy depth was found, which may provide the technical support for the qualitative appraisal of inner wall defect indication and its quantity.