Abstract: Rolling contact force between the wheel and the rail during the running of the locomotive causes the rolling fatigue cracks (RCF) appearing in wheel tread. The fatigue crack closes with the third medium filling in the crack gap, which causes the decreasing of probability of detection (POD). The crack region filled with the third medium has a weak conductivity, where the distribution of eddy current displays a different phenomenon comparing with opening crack. Based on the eddy current pulsed thermography (ECPT) method, the crack filled with corrosion was detected and its characteristics of the eddy current distribution had been studied in a weak conductance state. The detection of fatigue crack closure is studied and the difference of the eddy current distribution between open crack and closed crack during heating stage is compared in different depth through the simulation method. The oblique crack with corrosion is made and tested, and the results are in good agreement with the simulation results.