Abstract: The steam piping system of the power station has been in a high temperature and high pressure environment for a long time, which is prone to cracks and other defects and lead to destructive accidents. Conventional NDT methods are limited. Based on the ACFM, the variation law of the electromagnetic field on the surface of the workpiece is studied by simulation. High-temperature probes and test blocks are made and tested to verify the effectiveness of this method. The test results show that the on-line detection of high-temperature steam pipelines can be realized by using the ACFM.