Abstract: The theory of ultrasound guided wave detection and the principle of using guided wave on on-line monitoring were introduced. At the same time, we made use of the guided wave on 7 high temperature pipes in catalytic cracking unit, and took pipe 03-13 as an example to monitor its corrosion and analyze the data. Finally, conclusions were drawn that the magnetostrictive effect based guided wave technology allowed the monitoring of high temperature corrosion of pipe-line. In addition, the paper pointed out problems faced by ultrasonic guided wave monitoring technology and overviewed its future development.