Abstract: In order to solve the high temperature metal pipeline internal corrosion detection,a metal pipeline corrosion detecting instrument based on electromagnetic ultrasonic detection technology was developed.The instrument adopts the electromagnetic ultrasonic probe excitation of vertical incident wave or surface wave,and the corrosion state of the pipeline is obtained by measuring the wall thickness or by detecting reflection waves from the pipe wall corrosion defects.The instrument consists of electromagnetic ultrasonic probe,transmission and receiving circuits,digital signal processing circuit and corrosion detection analysis software components.Testing results were shown by “B” or “C” scanning images and were quantitatively analyzed.The instrument can help people to judge the corrosion state of inner wall of pipelines or tanks,providing the basis for safety production and assessment of pipeline.